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  • 1.
    Aizawa, S.
    et al.
    IRAP, CNRS-CNES-UPS, Toulouse, France; Graduate School of Science, Tohoku University, Sendai, Japan.
    Griton, L.S.
    IRAP, CNRS-CNES-UPS, Toulouse, France; LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, Meudon, France.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, Kiruna, Sweden.
    Exner, W.
    Institute for Geophysics and Extraterrestrial Physics, Technische Universität Braunschweig, Braunschweig, Germany; Institute for Theoretical Physics, Technische Universität Braunschweig, Braunschweig, Germany; School of Earth and Atmospheric Sciences, Georgia Institute of Technology, Atlanta, United States.
    Deca, J.
    Laboratory for Atmospheric and Space Physics (LASP), University of Colorado Boulder, CO, Boulder, United States; Institute for Modeling Plasma, Atmospheres and Cosmic Dust, NASA/SSERVI, CA, United States; Laboratoire Atmosphères, Milieux, Observations Spatiales (LATMOS), Université de Versailles à Saint Quentin, Guyancourt, France.
    Pantellini, F.
    LESIA, Observatoire de Paris, Université PSL, CNRS, Sorbonne Université, Université de Paris, 5 place Jules Janssen, Meudon, France.
    Yagi, M.
    RIKEN, Kobe, Japan.
    Heyner, D.
    Institute for Geophysics and Extraterrestrial Physics, Technische Universität Braunschweig, Braunschweig, Germany.
    Génot, V.
    IRAP, CNRS-CNES-UPS, Toulouse, France.
    André, N.
    IRAP, CNRS-CNES-UPS, Toulouse, France.
    Amaya, J.
    CmPA, Mathematics Department, KU Leuven, Belgium.
    Murakami, G.
    ISAS/JAXA, Sagamihara, Japan.
    Beigbeder, L.
    GFI, Toulouse, France.
    Gangloff, M.
    IRAP, CNRS-CNES-UPS, Toulouse, France.
    Bouchemit, M.
    IRAP, CNRS-CNES-UPS, Toulouse, France.
    Budnik, E.
    Noveltis, Toulouse, France.
    Usui, H.
    Kobe University, Kobe, Japan.
    Cross-comparison of global simulation models applied to Mercury's dayside magnetosphere2021In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 198, article id 105176Article in journal (Refereed)
    Abstract [en]

    We present the first comparison of multiple global simulations of the solar wind interaction with Mercury's dayside magnetosphere, conducted in the framework of the international collaborative project SHOTS - Studies on Hermean magnetosphere Oriented Theories and Simulations. Two 3D magnetohydrodynamic and two 3D hybrid simulation codes are used to investigate the global response of the Hermean magnetosphere without its exosphere to a northward-oriented interplanetary magnetic field. We cross-compare the results of the four codes for a theoretical case and a MESSENGER orbit with similar upstream plasma conditions. The models agree on bowshock and magnetopause locations at 2.1 ​± ​0.11 and 1.4 ​± ​0.1 Mercury planetary radii, respectively. The latter locations may be influenced by subtle differences in the treatment of the plasma boundary at the planetary surface. The predicted magnetosheath thickness varies less between the codes. Finally, we also sample the plasma data along virtual trajectories of BepiColombo's Magnetospheric and Planetary Orbiter. Our ability to accurately predict the structure of the Hermean magnetosphere aids the analysis of the onboard plasma measurements of past and future magnetospheric missions.

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  • 2.
    Alsakka, Abdullah
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cosmological Constraints for a Varying Dark Energy Model2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    This paper uses the Pantheon+ data set that consists of 1701 light curves of 1550 unique type IaSupernova to find constraints on various cosmological models and compare them with a varying darkenergy model proposed by Chevallier, Polarski and Linder in the early 2000s and analyze it deeper.The results show a tipping point from a decelerating universe to an accelerating one at a redshift ofz = 0.35, and a second tipping point back to a decelerating universe in the future at z = −0.19. The flatChevallier-Polarski-Linder (CPL) model leads to a matter dominated universe with Ωm = 0.52 ± 0.08while the relative dark energy density Ωde = 0.48±0.08. Finally, taking all these models and comparingthem with the results that are found from Taylor expanding the distance relation shows that they aremostly consistent with a deceleration parameter around q0 = −0.28.

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  • 3.
    Alí, Noor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    The Expansion of the Universe and Type Ia Supernovae: An analysis of PS1 SN Ia light-curve fits, distances, and redshifts. A Comparison of the PS1 Hubble Diagram with the ΛCDM cosmological model2023Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    Supernovae are the most spectacular explosions in the universe. They are very rare phenomena in a galaxy, occurring around three times per century in the Milky Way. This project points to the importance of type Ia supernovae as standard candles and their use in modern cosmology and they are being the current standard-bearers for dark energy.

    In this thesis, we attempt to understand open questions by looking at a large homogeneous sample of nearby SNe Ia from PanSTARRS1 (2018), for which we have 270 well-observed SNe Ia. The redshift relations to second order in the luminosity distance type Ia supernovae, also known as a Hubble diagram, could be explained by a hypothetical form of energy. This dark energy opposes the self-attraction of matter and causes the expansion of the Universe to accelerate.

    Pantheon SN data and Planck 2015 CMB measurements are combined, and the results are Ω𝑚=0.307±0.012 and 𝑤=−1.026 ± 0.041 for the 𝑤 CDM model. The results of the PS1 data show the most accurate measurement of dark energy to date: 𝑤0=−1.007±0.089 and 𝑤𝑎=−0.222±0.407 for the 𝑤0𝑤𝑎 CDM model with a value of a Hubble constant of H0 = 73.40+0.99 −1.22 km s−1 Mpc−1. We use these values to put the standardized SNe Ia on a Hubble diagram.

    We outline the procedures for standardizing SNe, to demonstrate that supernova properties rely on their environment, and to suggest adding a host galaxy (coupled with Cepheid distances to SN Ia host galaxies) term to the Hubble diagram.

  • 4.
    Andersson, Nils
    et al.
    School of Mathematics, University of Southampton.
    Haskell, Brynmore
    Astronomical Institute "Anton Pannekoek, University of Amsterdam.
    Samuelsson, Lars
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Lagrangian perturbation theory for a superfluid immersed in an elastic neutron star crust2011In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 416, no 1, p. 118-132Article in journal (Refereed)
    Abstract [en]

    The inner crust of mature neutron stars, where an elastic lattice of neutron-rich nuclei coexists with a neutron superfluid, impacts on a range of astrophysical phenomena. The presence of the superfluid is key to our understanding of pulsar glitches, and is expected to affect the thermal conductivity and hence the evolution of the surface temperature. The coupling between crust and superfluid must also be accounted for in studies of neutron star dynamics, discussions of global oscillations and associated instabilities. In this paper we develop Lagrangian perturbation theory for this problem, paying attention to key issues like superfluid entrainment, potential vortex pinning, dissipative mutual friction and the star's magnetic field. We also discuss the nature of the core-crust interface. The results provide a theoretical foundation for a range of interesting astrophysical applications.

  • 5.
    Bamford, R. A.
    et al.
    RAL Space, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, United Kingdom.
    Kellett, B.
    RAL Space, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, United Kingdom.
    Bradford, W. J.
    RAL Space, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, United Kingdom.
    Norberg, Carol
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, Box 812, SE-981 28 Kiruna, Sweden.
    Thornton, A.
    York Plasma Institute, Department of Physics, University of York, Heslington, York, YO10 5DD, United Kingdom.
    Gibson, K. J.
    York Plasma Institute, Department of Physics, University of York, Heslington, York, YO10 5DD, United Kingdom.
    Crawford, I. A.
    Department of Earth and Planetary Sciences, Birkbeck College, London, United Kingdom.
    Silva, L.
    Instituto Superior Técnico, 1049-00, Lisboa, Portugal.
    Gargate, L.
    Instituto Superior Técnico, 1049-00, Lisboa, Portugal.
    Bingham, Ruth
    University of Strathclyde, Glasgow, Scotland, United Kingdom and Central Laser Facility, Rutherford Appleton Laboratory, Chilton, Didcot, OX11 0QX, United Kingdom.
    Minimagnetospheres above the lunar surface and the formation of lunar swirls2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 109, no 8, p. 081101-Article in journal (Refereed)
    Abstract [en]

    In this paper we will present the in-situ satellite data, theory and laboratory validation that show how small scale collisionless shocks and mini-magnetospheres can form on the electron inertial scale length. The resulting retardation and deflection of the solar wind ions could be responsible for the unusual "lunar swirl" patterns seen on the surface of the Moon.

  • 6.
    Baqué, Mickael
    et al.
    Institute of Planetary Research, Planetary Laboratories Department, German Aerospace Center (DLR), Berlin, Germany.
    Backhaus, Theresa
    Heinrich-Heine-Universität (HHU), Institut für Botanik, Düsseldorf, Germany.
    Meeßen, Joachim
    Heinrich-Heine-Universität (HHU), Institut für Botanik, Düsseldorf, Germany.
    Hanke, Franziska
    Institute of Optical Sensor Systems, German Aerospace Center (DLR), Berlin, Germany.
    Böttger, Ute
    Institute of Optical Sensor Systems, German Aerospace Center (DLR), Berlin, Germany.
    Ramkissoon, Nisha
    Faculty of Science, Technology, Engineering and Mathematics, Open University, Milton Keynes, United Kingdom.
    Olsson-Francis, Karen
    Faculty of Science, Technology, Engineering and Mathematics, Open University, Milton Keynes, United Kingdom.
    Baumgärtner, Michael
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Billi, Daniela
    Department of Biology, University of Rome Tor Vergata, Via della Ricerca Scientifica, Rome, Italy.
    Cassaro, Alessia
    Department of Ecological and Biological Sciences (DEB), University of Tuscia, Largo dell'Università snc, Viterbo, Italy.
    de la Torre Noetzel, Rosa
    Departamento de Observación de la Tierra, Instituto Nacional de Técnica Aeroespacial (INTA), Madrid, Spain.
    Demets, René
    European Space Agency (ESA), European Space Research and Technology Centre (ESTEC), Noordwijk, Netherlands.
    Edwards, Howell
    University of Bradford, University Analytical Centre, Division of Chemical and Forensic Sciences, Raman Spectroscopy Group, West Yorkshire, United Kingdom.
    Ehrenfreund, Pascale
    Leiden Observatory, Laboratory Astrophysics, Leiden University, Leiden, Netherlands; George Washington University, Space Policy Institute, WA, United States.
    Elsaesser, Andreas
    Freie Universitaet Berlin, Experimental Biophysics and Space Sciences, Institute of Experimental Physics, Berlin, Germany.
    Foing, Bernard
    Leiden Observatory, Laboratory Astrophysics, Leiden University, Leiden, Netherlands; Faculty of Earth and Life Sciences, Vrije Universiteit Amsterdam, Amsterdam, Netherlands.
    Foucher, Frédéric
    CNRS Centre de Biophysique Moléculaire, Orléans, France.
    Huwe, Björn
    Biodiversity Research/Systematic Botany, University of Potsdam, Potsdam, Germany; Department Technology Assessment and Substance Cycles, Leibniz- Institute for Agriculture Engineering and Bioeconomy, Potsdam, Germany.
    Joshi, Jasmin
    Institute for Landscape and Open Space, Eastern Switzerland University of Applied Sciences, Rapperswil, Switzerland.
    Kozyrovska, Natalia
    Institute of Molecular Biology and Genetics of NASU, Kyiv, Ukraine.
    Lasch, Peter
    Centre for Biological Threats and Special Pathogens (ZBS 6), Robert Koch Institute, Berlin, Germany.
    Lee, Natuschka
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Leuko, Stefan
    Institute of Aerospace Medicine, Radiation Biology Department, German Aerospace Center (DLR), Linder Höhe, Germany.
    Onofri, Silvano
    Department of Ecological and Biological Sciences (DEB), University of Tuscia, Largo dell'Università snc, Viterbo, Italy.
    Ott, Sieglinde
    Heinrich-Heine-Universität (HHU), Institut für Botanik, Düsseldorf, Germany.
    Pacelli, Claudia
    Department of Ecological and Biological Sciences (DEB), University of Tuscia, Largo dell'Università snc, Viterbo, Italy; Research and Science Department, Italian Space Agency (ASI), Rome, Italy.
    Rabbow, Elke
    Institute of Aerospace Medicine, Radiation Biology Department, German Aerospace Center (DLR), Linder Höhe, Germany.
    Rothschild, Lynn
    NASA Ames Research Center, Moffett Field, CA, United States; Department of Molecular Biology, Cell Biology and Biochemistry, Brown University, Providence, USA.
    Schulze-Makuch, Dirk
    Technical University Berlin, Berlin, Germany; Section Geomicrobiology, German Research Centre for Geosciences (GFZ), Telegrafenberg, Potsdam, Germany; Department of Experimental Limnology, Leibniz-Institute of Freshwater Ecology and Inland Fisheries (IGB), Stechlin, Germany.
    Selbmann, Laura
    Department of Ecological and Biological Sciences (DEB), University of Tuscia, Largo dell'Università snc, Viterbo, Italy; Mycological Section, Italian Antarctic National Museum (MNA), Genoa, Italy.
    Serrano, Paloma
    Section Geomicrobiology, German Research Centre for Geosciences (GFZ), Telegrafenberg, Potsdam, Germany; Helmholtz Centre for Polar and Marine Research, Alfred Wegener Institute (AWI), Telegrafenberg, Potsdam, Germany.
    Szewzyk, Ulrich
    Institute of Environmental Technology, Environmental Microbiology, Technical University Berlin, Berlin, Germany.
    Verseux, Cyprien
    Center of Applied Space Technology and Microgravity (ZARM), University of Bremen, Bremen, Germany.
    Wagner, Dirk
    Section Geomicrobiology, German Research Centre for Geosciences (GFZ), Potsdam, Germany; Institute of Geosciences, University of Potsdam, Potsdam, Germany.
    Westall, Frances
    CNRS Centre de Biophysique Moléculaire, Orléans, France.
    Zucconi, Laura
    Department of Ecological and Biological Sciences (DEB), University of Tuscia, Largo dell'Università snc, Viterbo, Italy.
    de Vera, Jean-Pierre P
    Microgravity User Support Center (MUSC), German Aerospace Center (DLR), Linder Höhe, Germany.
    Biosignature stability in space enables their use for life detection on Mars2022In: Science Advances, E-ISSN 2375-2548, Vol. 8, no 36, article id eabn7412Article in journal (Refereed)
    Abstract [en]

    Two rover missions to Mars aim to detect biomolecules as a sign of extinct or extant life with, among other instruments, Raman spectrometers. However, there are many unknowns about the stability of Raman-detectable biomolecules in the martian environment, clouding the interpretation of the results. To quantify Raman-detectable biomolecule stability, we exposed seven biomolecules for 469 days to a simulated martian environment outside the International Space Station. Ultraviolet radiation (UVR) strongly changed the Raman spectra signals, but only minor change was observed when samples were shielded from UVR. These findings provide support for Mars mission operations searching for biosignatures in the subsurface. This experiment demonstrates the detectability of biomolecules by Raman spectroscopy in Mars regolith analogs after space exposure and lays the groundwork for a consolidated space-proven database of spectroscopy biosignatures in targeted environments.

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  • 7. Behar, E.
    et al.
    Tabone, B.
    Saillenfest, M.
    Henri, P.
    Deca, J.
    Lindkvist, Jesper
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Holmstrom, M.
    Nilsson, H.
    Solar wind dynamics around a comet: A 2D semi-analytical kinetic model2018In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 620, article id A35Article in journal (Refereed)
    Abstract [en]

    Aims. We aim at analytically modelling the solar wind proton trajectories during their interaction with a partially ionised cometary atmosphere, not in terms of bulk properties of the flow but in terms of single particle dynamics.

    Methods. We first derive a generalised gyromotion, in which the electric field is reduced to its motional component. Steady-state is assumed, and simplified models of the cometary density and of the electron fluid are used to express the force experienced by individual solar wind protons during the interaction.

    Results. A three-dimensional (3D) analytical expression of the gyration of two interacting plasma beams is obtained. Applying it to a comet case, the force on protons is always perpendicular to their velocity and has an amplitude proportional to 1/r2. The solar wind deflection is obtained at any point in space. The resulting picture presents a caustic of intersecting trajectories, and a circular region is found that is completely free of particles. The particles do not lose any kinetic energy and this absence of deceleration, together with the solar wind deflection pattern and the presence of a solar wind ion cavity, is in good agreement with the general results of the Rosetta mission.

    Conclusions. The qualitative match between the model and the in situ data highlights how dominant the motional electric field is throughout most of the interaction region for the solar wind proton dynamics. The model provides a simple general kinetic description of how momentum is transferred between these two collisionless plasmas. It also shows the potential of this semi-analytical model for a systematic quantitative comparison to the data.

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  • 8.
    Behar, Etienne
    et al.
    Solar System Physics And Space Technology, Swedish Institute Of Space Physics, Kiruna, Sweden; Laboratoire Lagrange, Observatoire De La Côte d'Azur, Université Côte d'Azur, Cnrs, Nice, France.
    Fatemi, Shahab
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Henri, Pierre
    Laboratoire Lagrange, Observatoire De La Côte d'Azur, Université Côte d'Azur, Cnrs, Nice, France; LPC2E, Orléans, France.
    Holmström, Mats
    Laboratoire Lagrange, Observatoire De La Côte d'Azur, Université Côte d'Azur, Cnrs, Nice, France.
    Menura: A code for simulating the interaction between a turbulent solar wind and solar system bodies2022In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 40, no 3, p. 281-297Article in journal (Refereed)
    Abstract [en]

    Despite the close relationship between planetary science and plasma physics, few advanced numerical tools allow bridging the two topics. The code Menura proposes a breakthrough towards the self-consistent modelling of these overlapping fields, in a novel two-step approach allowing for the global simulation of the interaction between a fully turbulent solar wind and various bodies of the solar system. This article introduces the new code and its two-step global algorithm, illustrated by a first example: the interaction between a turbulent solar wind and a comet.

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  • 9.
    Bello Arufe, Aaron
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gravitational Waves in General Relativity2017Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    In this paper, we write a summary about general relativity and, in particular,gravitational waves. We start by discussing the mathematics that generalrelativity uses, as well as the geometry in general relativity's spacetime. Afterwards,we explain linearized general relativity and derive the linearizedversions of Einstein's equations. From here, we construct wave solutionsand explain the polarization of gravitational waves. The quadrupole formulais derived, and generation and detection of gravitational waves is brie ydiscussed. Finally, LIGO and its latest discovery of gravitational waves isreviewed.

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  • 10.
    Benseguane, Selma
    et al.
    LGL-TPE, Cnrs, Université Lyon, Ucbl, Ensl, Villeurbanne, France.
    Guilbert-Lepoutre, Aurélie
    LGL-TPE, Cnrs, Université Lyon, Ucbl, Ensl, Villeurbanne, France.
    Lasue, Jérémie
    Irap, Université de Toulouse, Cnrs, Cnes, Ups, Toulouse, France.
    Besse, Sébastien
    Aurora Technology B.V. for the European Space Agency, Esac, Villanueva de la Canada, Madrid, Spain.
    Leyrat, Cédric
    Lesia, Observatoire de Paris, Cnrs, Sorbonne Univ., Univ. Paris-Diderot, Meudon, France.
    Beth, Arnaud
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Costa Sitjà, Marc
    Rhea System for the European Space Agency, Esac, Villanueva de la Canada, Madrid, Spain.
    Grieger, Björn
    Aurora Technology B.V. for the European Space Agency, Esac, Villanueva de la Canada, Madrid, Spain.
    Capria, Maria Teresa
    Istituto di Astrofísica e Planetologia Spaziali (IAPS), Inaf, Roma, Italy.
    Evolution of pits at the surface of 67P/Churyumov-Gerasimenko2022In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 668, article id A132Article in journal (Refereed)
    Abstract [en]

    Context. The observation of pits at the surface of comets offers the opportunity to take a glimpse into the properties and the mechanisms that shape a nucleus through cometary activity. If the origin of these pits is still a matter of debate, multiple studies have recently suggested that known phase transitions (such as volatile sublimation or amorphous water ice crystallization) alone could not have carved these morphological features on the surface of 67P/Churyumov-Gerasimenko (hereafter 67P).

    Aims. We want to understand how the progressive modification of 67P' s surface due to cometary activity might have affected the characteristics of pits and alcoves. In particular, we aim to understand whether signatures of the formation mechanism of these surface morphological features can still be identified.

    Methods. To quantify the amount of erosion sustained at the surface of 67P since it arrived on its currently observed orbit, we selected 380 facets of a medium-resolution shape model of the nucleus, sampling 30 pits and alcoves across the surface. We computed the surface energy balance with a high temporal resolution, including shadowing and self-heating contributions. We then applied a thermal evolution model to assess the amount of erosion sustained after ten orbital revolutions under current illumination conditions.

    Results. We find that the maximum erosion sustained after ten orbital revolutions is on the order of 80 m, for facets located in the southern hemisphere. We thus confirm that progressive erosion cannot form pits and alcoves, as local erosion is much lower than their observed depth and diameter. We find that plateaus tend to erode more than bottoms, especially for the deepest depressions, and that some differential erosion can affect their morphology. As a general rule, our results suggest that sharp morphological features tend to be erased by progressive erosion.

    Conclusions. This study supports the assumption that deep circular pits, such as Seth_01, are the least processed morphological features at the surface of 67P, or the best preserved since their formation.

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  • 11. Berthomier, M.
    et al.
    Fazakerley, A. N.
    Forsyth, C.
    Pottelette, R.
    Alexandrova, O.
    Anastasiadis, A.
    Aruliah, A.
    Blelly, P. -L
    Briand, C.
    Bruno, R.
    Canu, P.
    Cecconi, B.
    Chust, T.
    Daglis, I.
    Davies, J.
    Dunlop, M.
    Fontaine, D.
    Genot, V.
    Gustavsson, B.
    Haerendel, G.
    Hamrin, Maria
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hapgood, M.
    Hess, S.
    Kataria, D.
    Kauristie, K.
    Kemble, S.
    Khotyaintsev, Y.
    Koskinen, H.
    Lamy, L.
    Lanchester, B.
    Louarn, P.
    Lucek, E.
    Lundin, R.
    Maksimovic, M.
    Manninen, J.
    Marchaudon, A.
    Marghitu, O.
    Marklund, G.
    Milan, S.
    Moen, J.
    Mottez, F.
    Nilsson, H.
    Ostgaard, N.
    Owen, C. J.
    Parrot, M.
    Pedersen, A.
    Perry, C.
    Pincon, J. -L
    Pitout, F.
    Pulkkinen, T.
    Rae, I. J.
    Rezeau, L.
    Roux, A.
    Sandahl, I.
    Sandberg, I.
    Turunen, E.
    Vogt, J.
    Walsh, A.
    Watt, C. E. J.
    Wild, J. A.
    Yamauchi, M.
    Zarka, P.
    Zouganelis, I.
    Alfven: magnetosphere-ionosphere connection explorers2012In: Experimental astronomy, ISSN 0922-6435, E-ISSN 1572-9508, Vol. 33, no 2-3, p. 445-489Article in journal (Refereed)
    Abstract [en]

    The aurorae are dynamic, luminous displays that grace the night skies of Earth's high latitude regions. The solar wind emanating from the Sun is their ultimate energy source, but the chain of plasma physical processes leading to auroral displays is complex. The special conditions at the interface between the solar wind-driven magnetosphere and the ionospheric environment at the top of Earth's atmosphere play a central role. In this Auroral Acceleration Region (AAR) persistent electric fields directed along the magnetic field accelerate magnetospheric electrons to the high energies needed to excite luminosity when they hit the atmosphere. The "ideal magnetohydrodynamics" description of space plasmas which is useful in much of the magnetosphere cannot be used to understand the AAR. The AAR has been studied by a small number of single spacecraft missions which revealed an environment rich in wave-particle interactions, plasma turbulence, and nonlinear acceleration processes, acting on a variety of spatio-temporal scales. The pioneering 4-spacecraft Cluster magnetospheric research mission is now fortuitously visiting the AAR, but its particle instruments are too slow to allow resolve many of the key plasma physics phenomena. The Alfv,n concept is designed specifically to take the next step in studying the aurora, by making the crucial high-time resolution, multi-scale measurements in the AAR, needed to address the key science questions of auroral plasma physics. The new knowledge that the mission will produce will find application in studies of the Sun, the processes that accelerate the solar wind and that produce aurora on other planets.

  • 12.
    Beth, Arnaud
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Department of Physics, Imperial College London, London, UK.
    Altwegg, K.
    Balsiger, H.
    Berthelier, J. -J.
    Combi, M. R.
    De Keyser, J.
    Fiethe, B.
    Fuselier, S. A.
    Galand, M.
    Gombosi, T. I.
    Rubin, M.
    Semon, T.
    ROSINA ion zoo at Comet 67P2020In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 642, article id A27Article in journal (Refereed)
    Abstract [en]

    Context: The Rosetta spacecraft escorted Comet 67P/Churyumov-Gerasimenko for 2 yr along its journey through the Solar System between 3.8 and 1.24 au. Thanks to the high resolution mass spectrometer on board Rosetta, the detailed ion composition within a coma has been accurately assessed in situ for the very first time.

    Aims: Previous cometary missions, such as Giotto, did not have the instrumental capabilities to identify the exact nature of the plasma in a coma because the mass resolution of the spectrometers onboard was too low to separate ion species with similar masses. In contrast, the Double Focusing Mass Spectrometer (DFMS), part of the Rosetta Orbiter Spectrometer for Ion and Neutral Analysis on board Rosetta (ROSINA), with its high mass resolution mode, outperformed all of them, revealing the diversity of cometary ions.

    Methods: We calibrated and analysed the set of spectra acquired by DFMS in ion mode from October 2014 to April 2016. In particular, we focused on the range from 13–39 u q−1. The high mass resolution of DFMS allows for accurate identifications of ions with quasi-similar masses, separating 13C+ from CH+, for instance.

    Results: We confirm the presence in situ of predicted cations at comets, such as CHm+ (m = 1−4), HnO+ (n = 1−3), O+, Na+, and several ionised and protonated molecules. Prior to Rosetta, only a fraction of them had been confirmed from Earth-based observations. In addition, we report for the first time the unambiguous presence of a molecular dication in the gas envelope of a Solar System body, namely CO2++.

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  • 13.
    Bradley, Michael
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Forsberg, Mats
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Keresztes, Zoltán
    Gravitational Waves in Locally Rotationally Symmetric (LRS) Class II Cosmologies2017In: Universe, E-ISSN 2218-1997, Vol. 3, no 4, article id 69Article in journal (Refereed)
    Abstract [en]

    In this work we consider perturbations of homogeneous and hypersurface orthogonal cosmological backgrounds with local rotational symmetry (LRS), using a method based on the 1 + 1 + 2 covariant split of spacetime. The backgrounds, of LRS class II, are characterised by that the vorticity, the twist of the 2-sheets, and the magnetic part of the Weyl tensor all vanish. They include the flat Friedmann universe as a special case. The matter contents of the perturbed spacetimes are given by vorticity-free perfect fluids, but otherwise the perturbations are arbitrary and describe gravitational, shear, and density waves. All the perturbation variables can be given in terms of the time evolution of a set of six harmonic coefficients. This set decouples into one set of four coefficients with the density perturbations acting as source terms, and another set of two coefficients describing damped source-free gravitational waves with odd parity. We also consider the flat Friedmann universe, which has been considered by several others using the 1 + 3 covariant split, as a check of the isotropic limit. In agreement with earlier results we find a second-order wavelike equation for the magnetic part of the Weyl tensor which decouples from the density gradient for the flat Friedmann universes. Assuming vanishing vector perturbations, including the density gradient, we find a similar equation for the electric part of the Weyl tensor, which was previously unnoticed.                

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  • 14.
    Bradley, Michael
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Forsberg, Mats
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Keresztes, Zoltán
    University of Szeged.
    Gergely, László A´
    University of Szeged.
    Dunsby, Peter K S
    University of Cape Town.
    Perturbations of Kantowski-Sachs models2015In: Proceedings of the Thirteenth Marcel Grossman Meeting on General Relativity / [ed] Robert T Jantzen, Kjell Rosquist, Remo Ruffini, Singapore: World Scientific, 2015, p. 2547-2549Conference paper (Refereed)
    Abstract [en]

    Perturbations of Kantowski-Sachs models with a positive cosmological constant are considered in a harmonic decomposition, in the framework of gauge invariant 1+3 and 1+1+2covariant splits of spacetime. Scalar, vector and tensor modes are allowed, however they remain vorticity-free and of perfect fluid type. The dynamics is encompassed in six evolution equations for six harmonic coefficients.

  • 15. Brosch, Noah
    et al.
    Häggström, Ingemar
    Pellinen-Wannberg, Asta
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, Kiruna.
    EISCAT observations of meteors from the sporadic complex2013In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 434, no 4, p. 2907-2921Article in journal (Refereed)
    Abstract [en]

    We report meteor observation with the European Incoherent Scatter Scientific Association (EISCAT) radars obtained during a continuous 24-h period in 2009 December. The period, just after the Geminid meteor shower, was selected to have no strong meteor shower activity to allow a comparison with our previous observations collected during the 2008 Geminid shower. During the 2009 run, we used the very high frequency (VHF) and ultrahigh frequency systems, but most of the results presented here were derived from the VHF data. We discuss the statistical properties of the radar echoes, their Doppler velocity and altitude distributions, their radar cross-section, etc. We concentrate, as in our previous paper, on the population of high-altitude echoes, which we clearly detect, and discuss these specifically. We recognize a few echoes with positive Doppler velocities as produced by meteoroids that presumably entered the atmosphere at similar to grazing incidence angles and were leaving it when detected by radar. We detect meteor echoes with essentially zero Doppler velocity, reported here for the first time, which we interpret as meteoroids moving almost perpendicular to the beam and producing specular reflections off the meteor trail. We discuss meteors detected with tristatic measurements for which we find bunching in azimuth and depression angle that depends on the time of the day. Finally, we report again of the lack of extreme velocity meteors, a fact that weakens significantly the claim of the existence and abundance of interstellar meteors.

  • 16.
    Brout, Dillon
    et al.
    Center for Astrophysics, Harvard & Smithsonian, MA, Cambridge, United States.
    Scolnic, Dan
    Department of Physics, Duke University, NC, Durham, United States.
    Popovic, Brodie
    Department of Physics, Duke University, NC, Durham, United States.
    Riess, Adam G.
    Space Telescope Science Institute, MD, Baltimore, United States; Department of Physics and Astronomy, Johns Hopkins University, MD, Baltimore, United States.
    Carr, Anthony
    School of Mathematics and Physics, University of Queensland, QLD, Brisbane, Australia.
    Zuntz, Joe
    Institute for Astronomy, University of Edinburgh, Edinburgh, United Kingdom.
    Kessler, Rick
    Kavli Institute for Cosmological Physics, University of Chicago, IL, Chicago, United States; Department of Astronomy and Astrophysics, University of Chicago, IL, Chicago, United States.
    Davis, Tamara M.
    School of Mathematics and Physics, University of Queensland, QLD, Brisbane, Australia.
    Hinton, Samuel
    School of Mathematics and Physics, University of Queensland, QLD, Brisbane, Australia.
    Jones, David
    Department of Astronomy and Astrophysics, University of California, CA, Santa Cruz, United States.
    D’Arcy Kenworthy, W.
    Department of Physics and Astronomy, Johns Hopkins University, MD, Baltimore, United States.
    Peterson, Erik R.
    Department of Physics, Duke University, NC, Durham, United States.
    Said, Khaled
    School of Mathematics and Physics, University of Queensland, QLD, Brisbane, Australia.
    Taylor, Georgie
    Research School of Astronomy and Astrophysics, Australian National University, Canberra, Australia.
    Ali, Noor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Armstrong, Patrick
    Mt. Stromlo Observatory, The Research School of Astronomy and Astrophysics, Australian National University, ACT, Australia.
    Charvu, Pranav
    Department of Physics, Duke University, NC, Durham, United States.
    Dwomoh, Arianna
    Department of Physics, Duke University, NC, Durham, United States.
    Meldorf, Cole
    Department of Astronomy and Astrophysics, University of Chicago, IL, Chicago, United States.
    Palmese, Antonella
    Department of Physics, University of California, CA, Berkeley, United States.
    Qu, Helen
    Department of Physics and Astronomy, University of Pennsylvania, PA, Philadelphia, United States.
    Rose, Benjamin M.
    Department of Physics, Duke University, NC, Durham, United States.
    Sanchez, Bruno
    Department of Physics, Duke University, NC, Durham, United States.
    Stubbs, Christopher W.
    Center for Astrophysics, Harvard & Smithsonian, MA, Cambridge, United States; Department of Physics, Harvard University, MA, Cambridge, United States.
    Vincenzi, Maria
    Department of Physics, Duke University, NC, Durham, United States.
    Wood, Charlotte M.
    Department of Physics and Astronomy, University of Notre Dame, IN, Notre Dame, United States.
    Brown, Peter J.
    Department of Physics and Astronomy, Texas A&M University, TX, College Station, United States; George P. and Cynthia Woods Mitchell Institute for Fundamental Physics & Astronomy, TX, College Station, United States.
    Chen, Rebecca
    Department of Physics, Duke University, NC, Durham, United States.
    Chambers, Ken
    Institute of Astronomy, University of Hawaii, HI, Honolulu, United States.
    Coulter, David A.
    Department of Astronomy and Astrophysics, University of California, CA, Santa Cruz, United States.
    Dai, Mi
    Department of Physics and Astronomy, Johns Hopkins University, MD, Baltimore, United States.
    Dimitriadis, Georgios
    School of Physics, Trinity College Dublin, The University of Dublin, Ireland.
    Filippenko, Alexei V.
    Department of Astronomy, University of California, CA, Berkeley, United States.
    Foley, Ryan J.
    Department of Astronomy and Astrophysics, University of California, CA, Santa Cruz, United States.
    Jha, Saurabh W.
    Department of Physics and Astronomy, Rutgers, The State University of New Jersey, NJ, Piscataway, United States.
    Kelsey, Lisa
    Institute of Cosmology and Gravitation, University of Portsmouth, Portsmouth, United Kingdom.
    Kirshner, Robert P.
    Center for Astrophysics, Harvard & Smithsonian, MA, Cambridge, United States; Gordon and Betty Moore Foundation, CA, Palo Alto, United States.
    Möller, Anais
    Centre for Astrophysics & Supercomputing, Swinburne University of Technology, VIC, Australia; LPC, Université Clermont Auvergne, CNRS, IN2P3, Clermont-Ferrand, France.
    Muir, Jessie
    Perimeter Institute for Theoretical Physics, ON, Waterloo, Canada.
    Nadathur, Seshadri
    Department of Physics & Astronomy, University College London, London, United Kingdom.
    Pan, Yen-Chen
    Graduate Institute of Astronomy, National Central University, Jhongli, Taiwan.
    Rest, Armin
    Space Telescope Science Institute, MD, Baltimore, United States.
    Rojas-Bravo, Cesar
    Department of Astronomy and Astrophysics, University of California, CA, Santa Cruz, United States.
    Sako, Masao
    Department of Physics and Astronomy, University of Pennsylvania, PA, Philadelphia, United States.
    Siebert, Matthew R.
    Department of Astronomy and Astrophysics, University of California, CA, Santa Cruz, United States.
    Smith, Mat
    Université de Lyon, Université Claude Bernard Lyon 1, CNRS, IN2P3, IP2I Lyon, Villeurbanne, France.
    Stahl, Benjamin E.
    Department of Astronomy, University of California, CA, Berkeley, United States.
    Wiseman, Phil
    School of Physics and Astronomy, University of Southampton, Southampton, United Kingdom.
    The Pantheon+ analysis: cosmological constraints2022In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 938, no 2, article id 110Article in journal (Refereed)
    Abstract [en]

    We present constraints on cosmological parameters from the Pantheon+ analysis of 1701 light curves of 1550 distinct Type Ia supernovae (SNe Ia) ranging in redshift from z = 0.001 to 2.26. This work features an increased sample size from the addition of multiple cross-calibrated photometric systems of SNe covering an increased redshift span, and improved treatments of systematic uncertainties in comparison to the original Pantheon analysis, which together result in a factor of 2 improvement in cosmological constraining power. For a flat ΛCDM model, we find ΩM = 0.334 ± 0.018 from SNe Ia alone. For a flat w0CDM model, we measure w0 = −0.90 ± 0.14 from SNe Ia alone, H0 = 73.5 ± 1.1 km s−1 Mpc−1 when including the Cepheid host distances and covariance (SH0ES), and w0 = -0.978-+0.0310.024 when combining the SN likelihood with Planck constraints from the cosmic microwave background (CMB) and baryon acoustic oscillations (BAO); both w0 values are consistent with a cosmological constant. We also present the most precise measurements to date on the evolution of dark energy in a flat w0waCDM universe, and measure wa = -0.1-+2.00.9 from Pantheon+ SNe Ia alone, H0 = 73.3 ± 1.1 km s−1 Mpc−1 when including SH0ES Cepheid distances, and wa = -0.65-+0.320.28 when combining Pantheon+ SNe Ia with CMB and BAO data. Finally, we find that systematic uncertainties in the use of SNe Ia along the distance ladder comprise less than one-third of the total uncertainty in the measurement of H0 and cannot explain the present “Hubble tension” between local measurements and early universe predictions from the cosmological model.

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  • 17.
    Brout, Dillon
    et al.
    Center for Astrophysics, Harvard & Smithsonian, MA, Cambridge, United States.
    Taylor, Georgie
    Research School of Astronomy and Astrophysics, Australian National University, Canberra, Australia.
    Scolnic, Dan
    Department of Physics, Duke University, NC, Durham, United States.
    Wood, Charlotte M.
    Department of Physics, University of Notre Dame, IN, Notre Dame, United States.
    Rose, Benjamin M.
    Department of Physics, Duke University, NC, Durham, United States.
    Vincenzi, Maria
    Department of Physics, Duke University, NC, Durham, United States.
    Dwomoh, Arianna
    Department of Physics, Duke University, NC, Durham, United States.
    Lidman, Christopher
    The Research School of Astronomy and Astrophysics, Australian National University, ACT, Australia; Centre for Gravitational Astrophysics, College of Science, Australian National University, ACT, Australia.
    Riess, Adam
    Department of Physics and Astronomy, Johns Hopkins University, MD, Baltimore, United States.
    Ali, Noor
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Qu, Helen
    Department of Physics and Astronomy, University of Pennsylvania, PA, Philadelphia, United States.
    Dai, Mi
    Department of Physics and Astronomy, Johns Hopkins University, MD, Baltimore, United States.
    The Pantheon+ analysis: supercal-fragilistic cross calibration, retrained SALT2 light-curve model, and calibration systematic uncertainty2022In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 938, no 2, article id 111Article in journal (Refereed)
    Abstract [en]

    We present a recalibration of the photometric systems in the Pantheon+ sample of Type Ia supernovae (SNe Ia) including those in the SH0ES distance-ladder measurement of H0. We utilize the large and uniform sky coverage of the public Pan-STARRS stellar photometry catalog to cross calibrate against tertiary standards released by individual SN Ia surveys. The most significant updates over the “SuperCal” cross calibration used for the previous Pantheon and SH0ES analyses are: (1) expansion of the number of photometric systems (now 25) and filters (now 105), (2) solving for all filter offsets in all systems simultaneously to produce a calibration uncertainty covariance matrix for cosmological-model constraints, and (3) accounting for the change in the fundamental flux calibration of the Hubble Space Telescope CALSPEC standards from previous versions on the order of 1.5% over a Δλ of 4000 Å. We retrain the SALT2 model and find that our new model coupled with the new calibration of the light curves themselves causes a net distance modulus change (dμ/dz) of 0.04 mag over the redshift range 0 < z < 1. We introduce a new formalism to determine the systematic impact on cosmological inference by propagating the covariance in the fitted calibration offsets through retraining simultaneously with light-curve fitting and find a total calibration uncertainty impact of σw = 0.013; roughly half the size of the sample statistical uncertainty. Similarly, we find the systematic SN calibration contribution to the SH0ES H0 uncertainty is less than 0.2 km s−1 Mpc−1, suggesting that SN Ia calibration cannot resolve the current level of the “Hubble Tension.”

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  • 18.
    Canu Blot, Romain
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, Kiruna, Sweden.
    Wieser, Martin
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Wieser, Gabriella Stenberg
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Upper limit of the solar wind protons backscattering efficiency from Comet 67P/Churyumov-Gerasimenko2024In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 683, article id A245Article in journal (Refereed)
    Abstract [en]

    Context. Solar wind ions backscattering is a fundamental plasma-surface interaction process that may occur on all celestial bodies exposed to the solar wind and lacking a significant atmosphere or magnetosphere. Yet, observations have been limited to the regolith-covered Moon and Phobos, one of the Martian moons.

    Aims. We aim to expand our knowledge of the process to include comets by investigating the backscattering of solar wind protons from the surface of comet 67P/Churyumov-Gerasimenko.

    Methods. We used one of the ion spectrometers on board ESA s Rosetta spacecraft to search for evidence of backscattered solar wind protons from the cometary surface. The signal of interest was expected to be very weak and several statistical treatments of the data were essential to eliminate any influence from background noise and instrumental effects. Due to limited knowledge of the signal location within the observed parameter space, we conducted a statistical analysis to identify the most probable conditions for detecting the signal.

    Results. No significant solar wind backscattered protons were ever observed by the instrument. The statement applies to the large spectrum of observation conditions. An upper limit of the backscattered proton flux is given, as well as an upper limit of the backscattering efficiency of 9 A 104.

    Conclusions. The surface of comet 67P/Churyumov-Gerasimenko distinguishes itself as a notably weak reflector of solar wind protons, with its backscattering efficiency, at most, as large as the lowest observed backscattering efficiency from the lunar regolith.

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  • 19.
    Cetoli, Alberto
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Pethick, Christopher
    The Niels Bohr International Academy, The Niels Bohr Institute, Blegdamsvej 17, DK-2100 Copenhagen Ø, Denmark .
    Interaction of gravitational waves with normal and superconducting matter2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 85, no 6, p. 064036-Article in journal (Other academic)
    Abstract [en]

    We develop a unified formalism for describing the interaction of gravitational waves with matterthat clearly separates the effects of general relativity from those due to interactions in the matter.This allows one to take into account the microscopic character of the matter, and we derive a generalexpression for the dispersion of gravitational waves in matter in terms of correlation functions forthe matter in flat spacetime. The formalism enables one to derive simply previous results for thedispersion of gravitational waves in astrophysical plasmas. We also consider metals and show that,while simple estimates indicate that contributions of electrons to the stress tensor could be large,screening of the Coulomb interaction reduces these effects considerably. We consider both normaland superconducting metals, and show that in both cases, electrons and ions are locked togetherunder the influence of a gravitational wave with a frequency much less than the plasma frequencyand, consequently, charge separation has little effect on gravitational waves.

  • 20.
    Chong, Ghai Siung
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    De Spiegeleer, Alexandre
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hamrin, Maria
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Pitkänen, Timo
    Umeå University, Faculty of Science and Technology, Department of Physics. Institute of Space Sciences, Shandong University, Weihai, China; Space Physics and Astronomy Research Unit, University of Oulu, Oulu, Finland.
    Gunell, Herbert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Aizawa, S.
    Research Institute in Astrophysics and Planetology, Toulouse, France.
    Tailward Flows in the Vicinity of Fast Earthward Flows2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 4, article id e2020JA028978Article in journal (Refereed)
    Abstract [en]

    The occurrence of tailward flows in the magnetotail plasma sheet is closely linked to the dynamics of earthward bursty bulk flows (BBFs). Tailward flows that are observed in the vicinity of these BBFs (or TWABs – Tailward flows around BBFs) may hold unique information on its origin. In this study, we conduct a statistical survey on TWABs by using data from the Cluster mission. We find that TWABs are observed in the vicinity of ∼75% of the BBFs and their occurrence does not depend on BBF velocity magnitude. TWABs have a flow convection pattern consistent with the general tailward flows (GTWs) in the plasma sheet and they do not resemble vortical-like flows. However, TWABs have a flow velocity magnitude twice larger than the GTWs. The plasma density and temperature of TWABs are comparable with BBFs. It is more common to observe a TWAB succeeding than preceding a BBF. However, there is no distinctive difference (in flow pattern, plasma density and temperature) between preceding and succeeding TWABs. We suggest that TWABs are likely the “freshly” rebounded BBFs from the near-Earth region where the magnetic field is stronger. TWABs may represent the early stage of the evolution of tailward flows in the plasma sheet. We also discuss and argue that other mechanisms such as shear-induced vortical flows and tailward slipping of depleted flux tubes cannot be the principal causes of TWABs.

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  • 21.
    Chong, Ghai Siung
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Pitkänen, Timo
    Umeå University, Faculty of Science and Technology, Department of Physics. Institute of Space Sciences, Shandong University, Weihai, China.
    Hamrin, Maria
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schillings, Audrey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ion Convection as a Function of Distance to the Neutral Sheet in Earth's Magnetotail2021In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 126, no 12, article id e2021JA029694Article in journal (Refereed)
    Abstract [en]

    We utilized 33 years of data obtained by the Geotail, THEMIS, Cluster and MMS missions to investigate the slow (<200 km/s) ion flows perpendicular to the magnetic field in Earth's magnetotail plasma sheet. By using plasma β as a proxy of distance to the neutral sheet, we find that the ion flow patterns vary systematically within the plasma sheet. Particularly, in regions farther from the neutral sheet, earthward (tailward) flows exhibit a strong tendency to diverge (converge) quasi-symmetrically, with respect to the midnight meridional plane. As the distance becomes closer toward the neutral sheet, this tendency to diverge and converge gradually weakens. Moreover, duskward flows become the dominant components in both the earthward and tailward flows. These variations in ion flow patterns with distance to neutral sheet are hemispherically independent. We suggest that the spatial profiles of the electric and diamagnetic drift vary with distance to the neutral sheet and are therefore responsible for the varying ion flow patterns.

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  • 22.
    Daşdöğen, Dicle
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Cosmological Models in General Relativity2019Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
  • 23. de Vera, Jean-Pierre
    et al.
    Alawi, Mashal
    Backhaus, Theresa
    Baque, Mickael
    Billi, Daniela
    Boettger, Ute
    Berger, Thomas
    Bohmeier, Maria
    Cockell, Charles
    Demets, Rene
    de la Torre Noetzel, Rosa
    Edwards, Howell
    Elsaesser, Andreas
    Fagliarone, Claudia
    Fiedler, Annelie
    Foing, Bernard
    Foucher, Frederic
    Fritz, Joerg
    Hanke, Franziska
    Herzog, Thomas
    Horneck, Gerda
    Huebers, Heinz-Wilhelm
    Huwe, Bjoern
    Joshi, Jasmin
    Kozyrovska, Natalia
    Kruchten, Martha
    Lasch, Peter
    Lee, Natuschka
    Umeå University, Faculty of Science and Technology, Department of Ecology and Environmental Sciences.
    Leuko, Stefan
    Leya, Thomas
    Lorek, Andreas
    Martinez-Frias, Jesus
    Meessen, Joachim
    Moritz, Sophie
    Moeller, Ralf
    Olsson-Francis, Karen
    Onofri, Silvano
    Ott, Sieglinde
    Pacelli, Claudia
    Podolich, Olga
    Rabbow, Elke
    Reitz, Guenther
    Rettberg, Petra
    Reva, Oleg
    Rothschild, Lynn
    Garcia Sancho, Leo
    Schulze-Makuch, Dirk
    Selbmann, Laura
    Serrano, Paloma
    Szewzyk, Ulrich
    Verseux, Cyprien
    Wadsworth, Jennifer
    Wagner, Dirk
    Westall, Frances
    Wolter, David
    Zucconi, Laura
    Limits of Life and the Habitability of Mars: The ESA Space Experiment BIOMEX on the ISS2019In: Astrobiology, ISSN 1531-1074, E-ISSN 1557-8070, Vol. 19, no 2, p. 145-157Article in journal (Other academic)
    Abstract [en]

    BIOMEX (BIOlogy and Mars EXperiment) is an ESA/Roscosmos space exposure experiment housed within the exposure facility EXPOSE-R2 outside the Zvezda module on the International Space Station (ISS). The design of the multiuser facility supports-among others-the BIOMEX investigations into the stability and level of degradation of space-exposed biosignatures such as pigments, secondary metabolites, and cell surfaces in contact with a terrestrial and Mars analog mineral environment. In parallel, analysis on the viability of the investigated organisms has provided relevant data for evaluation of the habitability of Mars, for the limits of life, and for the likelihood of an interplanetary transfer of life (theory of lithopanspermia). In this project, lichens, archaea, bacteria, cyanobacteria, snow/permafrost algae, meristematic black fungi, and bryophytes from alpine and polar habitats were embedded, grown, and cultured on a mixture of martian and lunar regolith analogs or other terrestrial minerals. The organisms and regolith analogs and terrestrial mineral mixtures were then exposed to space and to simulated Mars-like conditions by way of the EXPOSE-R2 facility. In this special issue, we present the first set of data obtained in reference to our investigation into the habitability of Mars and limits of life. This project was initiated and implemented by the BIOMEX group, an international and interdisciplinary consortium of 30 institutes in 12 countries on 3 continents. Preflight tests for sample selection, results from ground-based simulation experiments, and the space experiments themselves are presented and include a complete overview of the scientific processes required for this space experiment and postflight analysis. The presented BIOMEX concept could be scaled up to future exposure experiments on the Moon and will serve as a pretest in low Earth orbit.

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  • 24.
    Degli Esposti, Gianluca
    et al.
    Helmholtz-Zentrum Dresdaen-Rossendorf, Dresden, Germany; Institut für Theoretische Physik, Technische Universität Dresden, Dresden, Germany.
    Torgrimsson, Greger
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Momentum spectrum of Schwinger pair production in four-dimensional e-dipole fields2024In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 109, no 1, article id 016013Article in journal (Refereed)
    Abstract [en]

    We calculate the momentum spectrum of electron-positron pairs created via the Schwinger mechanism by a class of four-dimensional electromagnetic fields called e-dipole fields. To the best of our knowledge, this is the first time the momentum spectrum has been calculated for 4D, exact solutions to Maxwell's equations. Moreover, these solutions give fields that are optimally focused, and are hence particularly relevant for future experiments. To achieve this we have developed a worldline instanton formalism where we separate the process into a formation and an acceleration region.

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  • 25.
    Degli Esposti, Gianluca
    et al.
    Helmholtz-Zentrum Dresden-Rossendorf, Dresden, Germany.
    Torgrimsson, Greger
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Worldline instantons for the momentum spectrum of Schwinger pair production in spacetime dependent fields2023In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 107, no 5, article id 056019Article in journal (Refereed)
    Abstract [en]

    We show how to use the worldline-instanton formalism to calculate the momentum spectrum of the electron-positron pairs produced by an electric field that depends on both space and time. Using the Lehmann-Symanzik-Zimmermann (LSZ) reduction formula with a worldline representation for the propagator in a spacetime field, we make use of the saddle-point method to obtain a semiclassical approximation of the pair-production spectrum. To check the final result, we integrate the spectrum and compare with the results obtained using a previous instanton method for the imaginary part of the effective action.

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  • 26. Dinu, Victor
    et al.
    Heinzl, Thomas
    Ilderton, Anton
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Infrared divergences in plane wave backgrounds2012In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 86, no 8, p. 085037-Article in journal (Refereed)
    Abstract [en]

    We show that the emission of soft photons via nonlinear Compton scattering in a pulsed plane wave (laser field) is in general infrared divergent. We give examples of both soft and soft-collinear divergences, and we pay particular attention to the case of crossed fields in both classical and quantum theories.

  • 27. Echim, M. M.
    et al.
    Lamy, H.
    De Keyser, J.
    Maggiolo, R.
    Gunell, Herbert
    Umeå University, Faculty of Science and Technology, Department of Physics. Royal Belgian Institute for Space Aeronomy, Brussels, Belgium.
    Wedlund, C. L. Simon
    A Method to Estimate the Physical Properties of Magnetospheric Generators From Observations of Quiet Discrete Auroral Arcs2019In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 12, p. 10283-10293Article in journal (Refereed)
    Abstract [en]

    We discuss a method to estimate the properties of a magnetospheric generator using a quasi-electrostatic magnetosphere-ionosphere coupling model and in situ or remote sensing observations of discrete quiet arcs. We first construct an ensemble of Vlasov equilibrium solutions for generator structures formed at magnetospheric plasma interfaces. For each generator solution, we compute the ionospheric electric potential from the current continuity equation. Thus, we estimate the field-aligned potential drop that allows us to assess several properties of the discrete auroral arc, such as the field-aligned potential difference, the field-aligned current density, the flux of precipitating energy, and the height-integrated Pedersen conductance. A minimization procedure based on comparing the numerical results with observations is defined and applied to find which solution of the current continuity equation and which generator model give auroral arc properties that best fit the observations. The procedure is validated in a case study with observations by DMSP and Cluster and can be generalized to other types of data.

  • 28.
    Edgar, S Brian
    et al.
    Linköpings Universitet.
    Bradley, Michael
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Machado Ramos, M Piedade
    Universidade do Minho, Guimarães.
    Symmetry analysis of radiative spacetimes with a null isotropy using GHP formalism2014In: General Relativity and Gravitation, ISSN 0001-7701, E-ISSN 1572-9532, Vol. 46, no 10, p. 1797-Article in journal (Refereed)
    Abstract [en]

    A complete and simple invariant classification of the conformally flat pure radiation metrics with a negative cosmological constant that were obtained by integration using the generalised invariant formalism is presented. We show equivalence between these metrics and the corresponding type O subclass of the more general spacetime studied by Siklos. The classification procedure indicates that the metrics possess a one degree of null isotropy freedom which has very interesting repercussions in the symmetry analysis. The Killing and homothetic vector analysis in GHP formalism is then generalised to this case were there is only one null direction defined geometrically. We determine the existing Killing vectors for the different subclasses that arise in the classification and compare these results to those obtained in the symmetry analysis performed by Siklos for a larger class of metrics with Ricci tensor representing a pure radiation field and a negative cosmological constant. It is also shown that there are no homothetic Killing vectors present.

  • 29.
    Ekenbäck, Andreas
    et al.
    Swedish Institute of Space Physics, P.O. Box 812, SE-98128 Kiruna, Sweden.
    Holmström, Mats
    Swedish Institute of Space Physics, P.O. Box 812, SE-98128 Kiruna, Sweden.
    Wurz, Peter
    Griessmeier, Jean-Mathias
    Lammer, Helmut
    Selsis, Franck
    Penz, Thomas
    Energetic neutral atoms around HD 209458b: estimations of magnetospheric properties2010In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 709, no 2, p. 670-679Article in journal (Refereed)
    Abstract [en]

    HD 209458b is an exoplanet found to transit the disk of its parent star. Observations have shown a broad absorption signature about the Ly alpha stellar line during transit, suggesting the presence of a thick cloud of atomic hydrogen around the "hot Jupiter" HD 209458b. This work expands on an earlier work studying the production of energetic neutral atoms (ENAs) as a result of the interaction between the stellar wind and the exosphere. We present an improved flow model of HD 209458b and use stellar wind values similar to those in our solar system. We find that the ENA production is high enough to explain the observations, and we show that-using expected values for the stellar wind and exosphere-the spatial and velocity distributions of ENAs would give absorption in good agreement with the observations. We also study how the production of ENAs depends on the exospheric parameters and establish an upper limit for the obstacle standoff distance at approximately 4-10 planetary radii. Finally, we compare the results obtained for the obstacle standoff distance with existing exomagnetospheric models and show how the magnetic moment of HD 209458b can be estimated from ENA observations.

  • 30.
    Ekman, Robin
    Umeå University, Faculty of Science and Technology, Department of Physics. Centre for Mathematical Sciences, University of Plymouth, Plymouth, United Kingdom.
    Reduction of order and transseries structure of radiation reaction2022In: Physical Review D: covering particles, fields, gravitation, and cosmology, ISSN 2470-0010, E-ISSN 2470-0029, Vol. 105, no 5, article id 056016Article in journal (Refereed)
    Abstract [en]

    The Landau-Lifshitz equation is obtained from the Lorentz-Abraham-Dirac equation through "reduction of order."It is the first in a divergent series of approximations that, after resummation, eliminate runaway solutions. Using Borel plane and transseries analysis we explain why this is, and show that a nonperturbative formulation of reduction of order can retain runaway solutions. We also apply transseries analysis to solutions of the Lorentz-Abraham-Dirac equation, essentially treating them as expansions in both time and a coupling. Our results illustrate some aspects of such expansions under changes of variables and limits.

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  • 31.
    Eliasson, Bengt
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics. Theoretische Physik IV, Ruhr–Universität Bochum, Bochum, Germany.
    Thidé, Bo
    Reply to comment by N. A. Gondarenko et al. on "Simulation study of the interaction between large-amplitude HF radio waves and the ionosphere"2007In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 34, no 23, article id L23105Article in journal (Refereed)
  • 32. Engebretson, Mark J.
    et al.
    Kirkevold, Kathryn R.
    Steinmetz, Erik S.
    Pilipenko, Viacheslav A.
    Moldwin, Mark B.
    McCuen, Brett A.
    Clauer, C. R.
    Hartinger, Michael D.
    Coyle, Shane
    Opgenoorth, Hermann J.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schillings, Audrey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Willer, Anna N.
    Edwards, Thom R.
    Boteler, David H.
    Gerrard, Andy J.
    Freeman, Mervyn P.
    Rose, Michael C.
    Interhemispheric Comparisons of Large Nighttime Magnetic Perturbation Events Relevant to GICs2020In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 125, no 8, article id e2020JA028128Article in journal (Refereed)
    Abstract [en]

    Nearly all studies of impulsive magnetic perturbation events (MPEs) with large magnetic field variability (dB/dt) that can produce dangerous geomagnetically induced currents (GICs) have used data from the Northern Hemisphere. Here we present details of four large‐amplitude MPE events (|ΔBx| > 900 nT and |dB/dt| > 10 nT/s in at least one component) observed between 2015 and 2018 in conjugate high‐latitude regions (65–80° corrected geomagnetic latitude), using magnetometer data from (1) Pangnirtung and Iqaluit in eastern Arctic Canada and the magnetically conjugate South Pole Station in Antarctica and (2) the Greenland West Coast Chain and two magnetically conjugate chains in Antarctica, AAL‐PIP and BAS LPM. From one to three different isolated MPEs localized in corrected geomagnetic latitude were observed during three premidnight events; many were simultaneous within 3 min in both hemispheres. Their conjugate latitudinal amplitude profiles, however, matched qualitatively at best. During an extended postmidnight interval, which we associate with an interval of omega bands, multiple highly localized MPEs occurred independently in time at each station in both hemispheres. These nighttime MPEs occurred under a wide range of geomagnetic conditions, but common to each was a negative interplanetary magnetic field Bz that exhibited at least a modest increase at or near the time of the event. A comparison of perturbation amplitudes to modeled ionospheric conductances in conjugate hemispheres clearly favored a current generator model over a voltage generator model for three of the four events; neither model provided a good fit for the premidnight event that occurred near vernal equinox.

  • 33.
    Engebretson, Mark J.
    et al.
    Augsburg University, MN, Minneapolis, United States.
    Pilipenko, Viacheslav A.
    Augsburg University, MN, Minneapolis, United States; Institute of Physics of the Earth, Moscow, Russian Federation.
    Steinmetz, Erik S.
    Augsburg University, MN, Minneapolis, United States.
    Moldwin, Mark B.
    University of Michigan, MI, Ann Arbor, United States.
    Connors, Martin G.
    Athabasca University, AB, Athabasca, Canada.
    Boteler, David H.
    Natural Resources Canada, ON, Ottawa, Canada.
    Singer, Howard J.
    NOAA Space Weather Prediction Center, CO, Boulder, United States.
    Opgenoorth, Hermann J.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Schillings, Audrey
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ohtani, Shin
    JHU/APL, MD, Laurel, United States.
    Gjerloev, Jesper
    JHU/APL, MD, Laurel, United States.
    Russell, Christopher T.
    UCLA Department of Earth Planetary and Space Sciences, CA, Los Angeles, United States.
    Nighttime Magnetic Perturbation Events Observed in Arctic Canada: 3. Occurrence and Amplitude as Functions of Magnetic Latitude, Local Time, and Magnetic Disturbance Indices2021In: Space Weather: The International Journal of Research and Application, E-ISSN 1542-7390, Vol. 19, no 3, article id e2020SW002526Article in journal (Refereed)
    Abstract [en]

    Rapid changes of magnetic fields associated with nighttime magnetic perturbation events (MPEs) with amplitudes |ΔB| of hundreds of nT and 5–10 min duration can induce geomagnetically induced currents (GICs) that can harm technological systems. This study compares the occurrence and amplitude of nighttime MPEs with |dB/dt| ≥ 6 nT/s observed during 2015 and 2017 at five stations in Arctic Canada ranging from 64.7° to 75.2° in corrected geomagnetic latitude (MLAT) as functions of magnetic local time (MLT), the SME (SuperMAG version of AE) and SYM/H magnetic indices, and time delay after substorm onsets. Although most MPEs occurred within 30 min after a substorm onset, ∼10% of those observed at the four lower latitude stations occurred over two hours after the most recent onset. A broad distribution in local time appeared at all five stations between 1700 and 0100 MLT, and a narrower distribution appeared at the lower latitude stations between 0200 and 0700 MLT. There was little or no correlation between MPE amplitude and the SYM/H index; most MPEs at all stations occurred for SYM/H values between −40 and 0 nT. SME index values for MPEs observed >1 h after the most recent substorm onset fell in the lower half of the range of SME values for events during substorms, and dipolarizations in synchronous orbit at GOES 13 during these events were weaker or more often nonexistent. These observations suggest that substorms are neither necessary nor sufficient to cause MPEs, and hence predictions of GICs cannot focus solely on substorms.

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  • 34.
    Fatemi, Shahab
    et al.
    Swedish Institute of Space Physics, Kiruna, Sweden ; Department of Computer Science, Electrical and Space Engineering, Division of Space Technology, Luleå University of Technology, Luleå, Sweden.
    Holmström, Mats
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Futaana, Yoshifumi
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Lue, Charles
    Umeå University, Faculty of Science and Technology, Department of Physics. Swedish Institute of Space Physics, Kiruna, Sweden.
    Collier, Michael R.
    NASA/Goddard Space Flight Center, Greenbelt, Maryland, USA.
    Barabash, Stas
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Stenberg, Gabriella
    Swedish Institute of Space Physics, Kiruna, Sweden.
    Effects of protons reflected by lunar crustal magnetic fields on the global lunar plasma environment2014In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 119, no 8, p. 6095-6105Article in journal (Refereed)
    Abstract [en]

    Solar wind plasma interaction with lunar crustal magnetic fields is different than that of magnetized bodies like the Earth. Lunar crustal fields are, for typical solar wind conditions, not strong enough to form a (bow) shock upstream but rather deflect and perturb plasma and fields. Here we study the global effects of protons reflected from lunar crustal magnetic fields on the lunar plasma environment when the Moon is in the unperturbed solar wind. We employ a three-dimensional hybrid model of plasma and an observed map of reflected protons from lunar magnetic anomalies over the lunar farside. We observe that magnetic fields and plasma upstream over the lunar crustal fields compress to nearly 120% and 160% of the solar wind, respectively. We find that these disturbances convect downstream in the vicinity of the lunar wake, while their relative magnitudes decrease. In addition, solar wind protons are disturbed and heated at compression regions and their velocity distribution changes from Maxwellian to a non-Maxwellian. Finally, we show that these features persists, independent of the details of the ion reflection by the magnetic fields.

  • 35. Fatemi, Shahab
    et al.
    Lue, Charles
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Holmstrom, Mats
    Poppe, Andrew R.
    Wieser, Martin
    Barabash, Stas
    Delory, Gregory T.
    Solar wind plasma interaction with Gerasimovich lunar magnetic anomaly2015In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 120, no 6, p. 4719-4735Article in journal (Refereed)
    Abstract [en]

    We present the results of the first local hybrid simulations (particle ions and fluid electrons) for the solar wind plasma interaction with realistic lunar crustal fields. We use a three-dimensional hybrid model of plasma and an empirical model of the Gerasimovich magnetic anomaly based on Lunar Prospector observations. We examine the effects of low and high solar wind dynamic pressures on this interaction when the Gerasimovich magnetic anomaly is located at nearly 20 degrees solar zenith angle. We find that for low solar wind dynamic pressure, the crustal fields mostly deflect the solar wind plasma, form a plasma void at very close distances to the Moon (below 20km above the surface), and reflect nearly 5% of the solar wind in charged form. In contrast, during high solar wind dynamic pressure, the crustal fields are more compressed, the solar wind is less deflected, and the lunar surface is less shielded from impinging solar wind flux, but the solar wind ion reflection is more locally intensified (up to 25%) compared to low dynamic pressures. The difference is associated with an electrostatic potential that forms over the Gerasimovich magnetic anomaly as well as the effects of solar wind plasma on the crustal fields during low and high dynamic pressures. Finally, we show that an antimoonward Hall electric field is the dominant electric field for similar to 3km altitude and higher, and an ambipolar electric field has a noticeable contribution to the electric field at close distances (<3km) to the Moon.

  • 36.
    Fatemi, Shahab
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Poppe, A.R.
    Space Sciences Laboratory, University of California at Berkeley, CA, Berkeley, United States.
    Vorburger, Audrey
    Umeå University, Faculty of Science and Technology, Department of Physics. Physics Institute, University of Bern, Bern, Switzerland.
    Lindkvist, Jesper
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Hamrin, Maria
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Ion Dynamics at the Magnetopause of Ganymede2022In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 127, no 1, article id e2021JA029863Article in journal (Refereed)
    Abstract [en]

    We study the dynamics of the thermal O+ and H+ ions at Ganymede's magnetopause when Ganymede is inside and outside of the Jovian plasma sheet using a three-dimensional hybrid model of plasma (kinetic ions, fluid electrons). We present the global structure of the electric fields and power density (E ⋅ J) in the magnetosphere of Ganymede and show that the power density at the magnetopause is mainly positive and on average is +0.95 and +0.75 nW/m3 when Ganymede is inside and outside the Jovian plasma sheet, respectively, but locally it reaches over +20 nW/m3. Our kinetic simulations show that ion velocity distributions at the vicinity of the upstream magnetopause of Ganymede are highly non-Maxwellian. We investigate the energization of the ions interacting with the magnetopause and find that the energy of those particles on average increases by a factor of 8 and 30 for the O+ and H+ ions, respectively. The energy of these ions is mostly within 1–100 keV for both species after interaction with the magnetopause, but a few percentages reach to 0.1–1 MeV. Our kinetic simulations show that a small fraction ((Formula presented.) 25%) of the corotating Jovian plasma reach the magnetopause, but among those >50% cross the high-power density regions at the magnetopause and gain energy. Finally, we compare our simulation results with Galileo observations of Ganymede's magnetopause crossings (i.e., G8 and G28 flybys). There is an excellent agreement between our simulations and observations, particularly our simulations fully capture the size and structure of the magnetosphere.

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  • 37.
    Fjellström, Benjamin
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gravitational Waves2021Independent thesis Basic level (degree of Bachelor), 10 credits / 15 HE creditsStudent thesis
    Abstract [en]

    The physics of gravitational waves have now entered a new era. Experimentally, we are now able to detect and study GW's, which has opened up an entirely new window of possibilities in areas of Astronomy and Cosmology. This paper is intended as an introduction to the basics of gravitational wave physics. First, the linearization of General Relativity is studied. Plane wave solution and their effects on test masses are analysed, and a formula for the energy carried by the GW's is derived. At the end follows a brief summary of the first ever detection of GW's, named "GW150914", and how this was achieved experimentally. 

     

  • 38.
    Forsberg, Mats
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gravitational perturbations in plasmas and cosmology2010Doctoral thesis, comprehensive summary (Other academic)
    Abstract [en]

    Gravitational perturbations can be in the form of scalars, vectors or tensors. This thesis focuses on the evolution of scalar perturbations in cosmology, and interactions between tensor perturbations, in the form of gravitational waves, and plasma waves.

    The gravitational waves studied in this thesis are assumed to have small amplitudes and wavelengths much shorter than the background length scale, allowing for the assumption of a flat background metric. Interactions between gravitational waves and plasmas are described by the Einstein-Maxwell-Vlasov, or the Einstein-Maxwell-fluid equations, depending on the level of detail required. Using such models, linear wave excitation of various waves by gravitational waves in astrophysical plasmas are studied, with a focus on resonance effects. Furthermore, the influence of strong magnetic field quantum electrodynamics, leading to detuning of the gravitational wave-electromagnetic wave resonances, is considered. Various nonlinear phenomena, including parametric excitation and wave steepening are also studied in different astrophysical settings.

    In cosmology the evolution of gravitational perturbations are of interest in processes such as structure formation and generation of large scale magnetic fields. Here, the growth of density perturbations in Kantowski-Sachs cosmologies with positive cosmological constant is studied.

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  • 39.
    Forsberg, Mats
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Brodin, Gert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Linear theory of gravitational wave propagation in a magnetized, relativistic Vlasov plasma2010In: Physical Review D, ISSN 1550-7998, E-ISSN 1550-2368, Vol. 82, no 12, article id 124029Article in journal (Refereed)
    Abstract [en]

    We consider propagation of gravitational waves in a magnetized plasma, using the linearized Maxwell-Vlasov equations coupled to Einstein's equations. A set of coupled electromagnetic-gravitational wave equations are derived that can be straightforwardly reduced to a single dispersion relation. We demonstrate that there is a number of different resonance effects that can enhance the influence of the plasma on the gravitational waves.

  • 40. Futaana, Y
    et al.
    Barabash, S
    Wieser, M
    Lue, C
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Wurz, P
    Vorburger, A
    Bhardwaj, A
    Asamura, K
    Remote energetic neutral atom imaging of electric potential over a lunar magnetic anomaly2013In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 40, no 2, p. 262-266Article in journal (Refereed)
    Abstract [en]

    The formation of electric potential over lunar magnetized regions is essential for understanding fundamental lunar science, for understanding the lunar environment, and for planning human exploration on the Moon. A large positive electric potential was predicted and detected from single point measurements. Here, we demonstrate a remote imaging technique of electric potential mapping at the lunar surface, making use of a new concept involving hydrogen neutral atoms derived from solar wind. We apply the technique to a lunar magnetized region using an existing dataset of the neutral atom energy spectrometer SARA/CENA on Chandrayaan-1. Electrostatic potential larger than +135 V inside the Gerasimovic anomaly is confirmed. This structure is found spreading all over the magnetized region. The widely spread electric potential can influence the local plasma and dust environment near the magnetic anomaly. Citation: Futaana, Y., S. Barabash, M. Wieser, C. Lue, P. Wurz, A. Vorburger, A. Bhardwaj, and K. Asamura (2013), Remote energetic neutral atom imaging of electric potential over a lunar magnetic anomaly, Geophys. Res. Lett., 40, 262-266, doi:10.1002/grl.50135.

  • 41.
    Gabrielsson, Jonas
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Estimation of satellite orbits using ground based radar concept2021Independent thesis Advanced level (professional degree), 20 credits / 30 HE creditsStudent thesis
    Abstract [en]

    Today an abundance of objects are circulating in earth captured orbit. Monitoring these objects is of national security interest. One way to map any object in orbit is with their Keplerian elements. A method for estimating the Keplerian elements of a satellite orbit simulating a ground based radar station has been investigated. A frequency modulated continuous wave radar (FMCW) with a central transmitter antenna and a grid of receivers was modeled in MATLAB. The maximum likelihood estimator (MLE) was obtained to estimate the parameters from the received signal. The method takes advantage of the relations between the Cartesian position and velocity and the Keplerian elements to confine the search space. For a signal to noise ratio (SNR) of 10dB, the satellite was followed during a time period of 0.1s where the positions were found within average error of range: ±1.4m, azimuth: ±2.0·10−6 rad and elevation: ±8.4·10−7 rad. Using a linear approximation of the velocity the Keplerian elements were found within average error of i: ±0.0050 rad, Ω:±0.0050 rad, ω: ±0.0058 rad, a: ±2.60·105m, e:±0.0021 and ν: ±0.24 rad. A method to obtain more accurate estimates is proposed.

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  • 42. Glampedakis, K.
    et al.
    Jones, D. I.
    Samuelsson, Lars
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gravitational Waves from Color-Magnetic "Mountains" in Neutron Stars2012In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 109, no 8, p. 081103-Article in journal (Refereed)
    Abstract [en]

    Neutron stars may harbor the true ground state of matter in the form of strange quark matter. If present, this type of matter is expected to be a color superconductor, a consequence of quark pairing with respect to the color and flavor degrees of freedom. The stellar magnetic field threading the quark core becomes a color-magnetic admixture and, in the event that superconductivity is of type II, leads to the formation of color-magnetic vortices. In this Letter, we show that the volume-averaged color-magnetic vortex tension force should naturally lead to a significant degree of nonaxisymmetry in systems such as radio pulsars. We show that gravitational radiation from such color-magnetic "mountains" in young pulsars, such as the Crab and Vela, could be observable by the future Einstein Telescope, thus, becoming a probe of paired quark matter in neutron stars. The detectability threshold can be pushed up toward the sensitivity level of Advanced LIGO if we invoke an interior magnetic field about a factor ten stronger than the surface polar field.

  • 43. Glampedakis, Kostas
    et al.
    Andersson, Nils
    Samuelsson, Lars
    Umeå University, Faculty of Science and Technology, Department of Physics. Nordita, Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden.
    Magnetohydrodynamics of superfluid and superconducting neutron star cores2011In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 410, no 2, p. 805-829Article in journal (Refereed)
    Abstract [en]

    Mature neutron stars are cold enough to contain a number of superfluid and superconducting components. These systems are distinguished by the presence of additional dynamical degrees of freedom associated with superfluidity. In order to consider models with mixtures of condensates, we need to develop a multifluid description that accounts for the presence of rotational neutron vortices and magnetic proton fluxtubes. We also need to model the forces that impede the motion of vortices and fluxtubes, and understand how these forces act on the condensates. This paper concerns the development of such a model for the outer core of a neutron star, where superfluid neutrons co-exist with a type II proton superconductor and an electron gas. We discuss the hydrodynamics of this system, focusing on the role of the entrainment effect, the magnetic field, the vortex/fluxtube tension and the dissipative mutual friction forces. Our final results can be directly applied to a number of interesting astrophysical scenarios, e.g. associated with neutron star oscillations or the evolution of the large-scale magnetic field.

  • 44.
    Glampedakis, Kostas
    et al.
    Theoretical Astrophysics, University of Tübingen.
    Jones, D. Ian
    School of Mathematics, University of Southampton.
    Samuelsson, Lars
    Umeå University, Faculty of Science and Technology, Department of Physics. Nordita, Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden.
    Ambipolar diffusion in superfluid neutron stars2011In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 413, no 3, p. 2021-2030Article in journal (Other academic)
    Abstract [en]

    In this paper we reconsider the problem of magnetic field diffusion in neutron star cores. We model the star as consisting of a mixture of neutrons, protons and electrons, and allow for particle reactions and binary collisions between species. Our analysis is in much the same spirit as that of Goldreich & Reisenegger (1992), and we content ourselves with rough estimates of magnetic diffusion timescales, rather than solving accurately for some particular field geometry. However, our work improves upon previous treatments in one crucial respect: we allow for superfluidity in the neutron star matter. We find that the consequent mutual friction force, coupling the neutrons and charged particles, together with the suppression of particles collisions and reactions, drastically affect the ambipolar magnetic field diffusion timescale. In particular, the addition of superfluidity means that it is unlikely that there is ambipolar diffusion in magnetar cores on the timescale of the lifetimes of these objects, contradicting an assumption often made in the modelling of the flaring activity commonly observed in magnetars. Our work suggests that if a decaying magnetic field is indeed the cause of magnetar activity, the field evolution is likely to take place outside of the core, and might represent Hall/Ohmic diffusion in the stellar crust, or else that a mechanism other than standard ambipolar diffusion is active, e.g. flux expulsion due to the interaction between neutron vortices and magnetic fluxtubes.

  • 45. Goetz, C.
    et al.
    Gunell, Herbert
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Volwerk, M.
    Beth, A.
    Eriksson, A.
    Galand, M.
    Henri, P.
    Nilsson, H.
    Wedlund, C. Simon
    Alho, M.
    Andersson, L.
    Andre, N.
    De Keyser, J.
    Deca, J.
    Ge, Y.
    Glassmeier, K.-H.
    Hajra, R.
    Karlsson, T.
    Kasahara, S.
    Kolmasova, I.
    LLera, K.
    Madanian, H.
    Mann, I.
    Mazelle, C.
    Odelstad, E.
    Plaschke, F.
    Rubin, M.
    Sanchez-Cano, B.
    Snodgrass, C.
    Vigren, E.
    Cometary plasma science: Open science questions for future space missions2022In: Experimental astronomy, ISSN 0922-6435, E-ISSN 1572-9508, Vol. 54, p. 1129-1167Article in journal (Refereed)
    Abstract [en]

    Comets hold the key to the understanding of our Solar System, its formation and its evolution, and to the fundamental plasma processes at work both in it and beyond it. A comet nucleus emits gas as it is heated by the sunlight. The gas forms the coma, where it is ionised, becomes a plasma, and eventually interacts with the solar wind. Besides these neutral and ionised gases, the coma also contains dust grains, released from the comet nucleus. As a cometary atmosphere develops when the comet travels through the Solar System, large-scale structures, such as the plasma boundaries, develop and disappear, while at planets such large-scale structures are only accessible in their fully grown, quasi-steady state. In situ measurements at comets enable us to learn both how such large-scale structures are formed or reformed and how small-scale processes in the plasma affect the formation and properties of these large scale structures. Furthermore, a comet goes through a wide range of parameter regimes during its life cycle, where either collisional processes, involving neutrals and charged particles, or collisionless processes are at play, and might even compete in complicated transitional regimes. Thus a comet presents a unique opportunity to study this parameter space, from an asteroid-like to a Mars- and Venus-like interaction. The Rosetta mission and previous fast flybys of comets have together made many new discoveries, but the most important breakthroughs in the understanding of cometary plasmas are yet to come. The Comet Interceptor mission will provide a sample of multi-point measurements at a comet, setting the stage for a multi-spacecraft mission to accompany a comet on its journey through the Solar System. This White Paper, submitted in response to the European Space Agency’s Voyage 2050 call, reviews the present-day knowledge of cometary plasmas, discusses the many questions that remain unanswered, and outlines a multi-spacecraft European Space Agency mission to accompany a comet that will answer these questions by combining both multi-spacecraft observations and a rendezvous mission, and at the same time advance our understanding of fundamental plasma physics and its role in planetary systems.

  • 46.
    Goncharov, Oleksandr
    et al.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Gunell, Herbert
    Umeå University, Faculty of Science and Technology, Department of Physics. Royal Belgian Institute of Space Aeronomy, Brussels, Belgium.
    Hamrin, Maria
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Chong, G. S.
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Evolution of High-Speed Jets and Plasmoids Downstream of the Quasi-Perpendicular Bow Shock2020In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 125, no 6, article id e2019JA027667Article in journal (Refereed)
    Abstract [en]

    Plasma structures with enhanced dynamic pressure, density, or speed are often observed in Earth's magnetosheath. We present a statistical study of these structures, known as jets and fast plasmoids, in the magnetosheath, downstream of both the quasi-perpendicular and quasi-parallel bow shocks. Using measurements from the four Magnetospheric Multiscale (MMS) spacecraft and OMNI solar wind data from 2015-2017, we present observations of jets during different upstream conditions and in the wide range of distances from the bow shock. Jets observed downstream of the quasi-parallel bow shock are seen to propagate deeper and faster into the magnetosheath and on toward the magnetopause. We estimate the shape of the structures by treating the leading edge as a shock surface, and the result is that the jets are elongated in the direction of propagation but also that they expand more quickly in the perpendicular direction as they propagate through the magnetosheath.

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  • 47.
    Gordon, I.E.
    et al.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Rothman, L.S.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Hargreaves, R.J.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Hashemi, R.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Karlovets, E.V.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Skinner, F.M.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Conway, E.K.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Hill, C.
    Nuclear Data Section, International Atomic Energy Agency, Vienna International Centre, PO Box 100, Vienna, Austria.
    Kochanov, R.V.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation; QUAMER laboratory, Tomsk State University, Tomsk, Russian Federation.
    Tan, Y.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Hefei National Laboratory for Physical Science at Microscale, University of Science and Technology of China, Hefei, China.
    Wcisło, P.
    Institute of Physics, Faculty of Physics, Astronomy and Informatics, Nicolaus Copernicus University in Torun, Grudziadzka 5, Torun, Poland.
    Finenko, A.A.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Department of Chemistry, Lomonosov Moscow State University, Moscow, Russian Federation.
    Nelson, K.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Bernath, P.F.
    Department of Chemistry, Old Dominion University, VA, Norfolk, United States.
    Birk, M.
    German Aerospace Center (DLR), Remote Sensing Technology Institute, Wessling, Germany.
    Boudon, V.
    Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne Franche-Comté, UMR 6303 CNRS, Dijon Cedex, France.
    Campargue, A.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Chance, K.V.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Coustenis, A.
    Laboratoire d'Etudes Spatiales et d'Instrumentation en Astrophysique, Paris Observatory, CNRS, PSL University, Sorbonne University, Paris, France.
    Drouin, B.J.
    Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Flaud, J.M.
    Institut des Sciences Moléculaires d'Orsay, CNRS, Université Paris-Sud, Université Paris-Saclay, Orsay, France.
    Gamache, R.R.
    Department of Environmental, Earth & Atmospheric Sciences, University of Massachusetts, MA, Lowell, United States.
    Hodges, J.T.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Jacquemart, D.
    Sorbonne Université, CNRS, De la MOlécule aux NAno-objets : Réactivité, Interactions et Spectroscopies, MONARIS, Paris, France.
    Mlawer, E.J.
    Atmospheric and Environmental Research, MA, Lexington, United States.
    Nikitin, A.V.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Perevalov, V.I.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Rotger, M.
    Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Tennyson, J.
    Department of Physics and Astronomy, University College London, London, United Kingdom.
    Toon, G.C.
    Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Tran, H.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique, Paris, France.
    Tyuterev, V.G.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation; QUAMER laboratory, Tomsk State University, Tomsk, Russian Federation; Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Adkins, E.M.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Baker, A.
    Division of Astronomy, California Institute of Technology, CA, Pasadena, United States.
    Barbe, A.
    Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Canè, E.
    Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale Risorgimento 4, Bologna, Italy.
    Császár, A.G.
    MTA-ELTE Complex Chemical Systems Research Group, Budapest, Hungary; Eötvös Loránd University, Institute of Chemistry, Budapest, Hungary.
    Dudaryonok, A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Egorov, O.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Fleisher, A.J.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Fleurbaey, H.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Foltynowicz, Aleksandra
    Umeå University, Faculty of Science and Technology, Department of Physics.
    Furtenbacher, T.
    MTA-ELTE Complex Chemical Systems Research Group, Budapest, Hungary.
    Harrison, J.J.
    Department of Physics and Astronomy, University of Leicester, Leicester, United Kingdom; University of Leicester, National Centre for Earth Observation, Leicester, United Kingdom; University of Leicester, Leicester Institute for Space and Earth Observation, Leicester, United Kingdom.
    Hartmann, J.M.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, École polytechnique, Sorbonne Université, École normale supérieure, PSL Research University, Palaiseau, France.
    Horneman, V.M.
    Department of Physics, University of Oulu, Finland.
    Huang, X.
    SETI Institute, CA, Mountain View, United States.
    Karman, T.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States.
    Karns, J.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Golisano College of Computing and Information Sciences, Rochester Institute of Technology, NY, Rochester, United States; Computer Science Department, State University of New York at Oswego, NY, Oswego, United States.
    Kassi, S.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Kleiner, I.
    Université de Paris and Univ Paris Est Creteil, CNRS, LISA, Paris, France.
    Kofman, V.
    NASA Goddard Space Flight Center, MD, Greenbelt, United States.
    Kwabia-Tchana, F.
    Université de Paris and Univ Paris Est Creteil, CNRS, LISA, Paris, France.
    Lavrentieva, N.N.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Lee, T.J.
    Planetary Systems Branch, Space Science and Astrobiology Division, NASA Ames Research Center, CA, Moffett Field, United States.
    Long, D.A.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Lukashevskaya, A.A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Lyulin, O.M.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Makhnev, V.Yu.
    Institute of Applied Physics of Russian Academy of Sciences, Nizhny Novgorod, Russian Federation.
    Matt, W.
    Center for Astrophysics |Harvard & Smithsonian, Atomic and Molecular Physics Division, MA, Cambridge, United States; Computer Science Department, State University of New York at Oswego, NY, Oswego, United States.
    Massie, S.T.
    University of Colorado, Laboratory for Atmospheric and Space Physics, CO, Boulder, United States.
    Melosso, M.
    Dipartimento di Chimica “Giacomo Ciamician”, Università di Bologna, Via F. Selmi 2, Bologna, Italy.
    Mikhailenko, S.N.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Mondelain, D.
    University of Grenoble Alpes, CNRS, LIPhy, Grenoble, France.
    Müller, H.S.P.
    I. Physikalisches Institut, Universität zu Köln, Köln, Germany.
    Naumenko, O.V.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Perrin, A.
    Laboratoire de Météorologie Dynamique/IPSL, CNRS, Sorbonne Université, École normale supérieure, PSL Research University, École polytechnique, Paris, France.
    Polyansky, O.L.
    Department of Physics and Astronomy, University College London, London, United Kingdom; Institute of Applied Physics of Russian Academy of Sciences, Nizhny Novgorod, Russian Federation.
    Raddaoui, E.
    Sorbonne Université, CNRS, De la MOlécule aux NAno-objets : Réactivité, Interactions et Spectroscopies, MONARIS, Paris, France.
    Raston, P.L.
    Department of Chemistry and Biochemistry, James Madison University, VA, Harrisonburg, United States; Department of Chemistry, University of Adelaide, South Australia, Australia.
    Reed, Z.D.
    Chemical Sciences Division, National Institute of Standards and Technology, MD, Gaithersburg, United States.
    Rey, M.
    Groupe de Spectrométrie Moléculaire et Atmosphérique, UMR CNRS 7331, BP 1039, Reims Cedex 2, France.
    Richard, C.
    Laboratoire Interdisciplinaire Carnot de Bourgogne, Université de Bourgogne Franche-Comté, UMR 6303 CNRS, Dijon Cedex, France.
    Tóbiás, R.
    MTA-ELTE Complex Chemical Systems Research Group, Budapest, Hungary.
    Sadiek, I.
    Umeå University, Faculty of Science and Technology, Department of Physics. Leibniz Institute for Plasma Science and Technology (INP), Greifswald, Germany.
    Schwenke, D.W.
    Planetary Systems Branch, Space Science and Astrobiology Division, NASA Ames Research Center, CA, Moffett Field, United States.
    Starikova, E.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Sung, K.
    Jet Propulsion Laboratory, California Institute of Technology, CA, Pasadena, United States.
    Tamassia, F.
    Dipartimento di Chimica Industriale “Toso Montanari”, Università di Bologna, Viale Risorgimento 4, Bologna, Italy.
    Tashkun, S.A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Vander Auwera, J.
    Université Libre de Bruxelles, Spectroscopy, Quantum Chemistry and Atmospheric Remote Sensing (SQUARES), C.P. 160/09, Brussels, Belgium.
    Vasilenko, I.A.
    V.E. Zuev Institute of Atmospheric Optics, Laboratory of Theoretical Spectroscopy, Russian Academy of Sciences, Tomsk, Russian Federation.
    Vigasin, A.A.
    Obukhov Institute of Atmospheric Physics, Russian Academy of Sciences, Pyzhevsky per. 3, Moscow, Russian Federation.
    Villanueva, G.L.
    NASA Goddard Space Flight Center, MD, Greenbelt, United States.
    Vispoel, B.
    Department of Environmental, Earth & Atmospheric Sciences, University of Massachusetts, MA, Lowell, United States; Research Unit Lasers and Spectroscopies (LLS), Institute of Life, Earth and Environment (ILEE), University of Namur (UNamur), Namur, Belgium; Royal Belgian Institute for Space Aeronomy (BIRA-IASB), Brussels, Belgium.
    Wagner, G.
    German Aerospace Center (DLR), Remote Sensing Technology Institute, Wessling, Germany.
    Yachmenev, A.
    Center for Free-Electron Laser Science, Deutsches Elektronen-Synchrotron DESY, Notkestraße 85, Hamburg, Germany; Hamburg Center for Ultrafast Imaging, Universität Hamburg, Luruper Chaussee 149, Hamburg, Germany.
    Yurchenko, S.N.
    Department of Physics and Astronomy, University College London, London, United Kingdom.
    The HITRAN2020 molecular spectroscopic database2022In: Journal of Quantitative Spectroscopy and Radiative Transfer, ISSN 0022-4073, E-ISSN 1879-1352, Vol. 277, article id 107949Article in journal (Refereed)
    Abstract [en]

    The HITRAN database is a compilation of molecular spectroscopic parameters. It was established in the early 1970s and is used by various computer codes to predict and simulate the transmission and emission of light in gaseous media (with an emphasis on terrestrial and planetary atmospheres). The HITRAN compilation is composed of five major components: the line-by-line spectroscopic parameters required for high-resolution radiative-transfer codes, experimental infrared absorption cross-sections (for molecules where it is not yet feasible for representation in a line-by-line form), collision-induced absorption data, aerosol indices of refraction, and general tables (including partition sums) that apply globally to the data. This paper describes the contents of the 2020 quadrennial edition of HITRAN. The HITRAN2020 edition takes advantage of recent experimental and theoretical data that were meticulously validated, in particular, against laboratory and atmospheric spectra. The new edition replaces the previous HITRAN edition of 2016 (including its updates during the intervening years). All five components of HITRAN have undergone major updates. In particular, the extent of the updates in the HITRAN2020 edition range from updating a few lines of specific molecules to complete replacements of the lists, and also the introduction of additional isotopologues and new (to HITRAN) molecules: SO, CH3F, GeH4, CS2, CH3I and NF3. Many new vibrational bands were added, extending the spectral coverage and completeness of the line lists. Also, the accuracy of the parameters for major atmospheric absorbers has been increased substantially, often featuring sub-percent uncertainties. Broadening parameters associated with the ambient pressure of water vapor were introduced to HITRAN for the first time and are now available for several molecules. The HITRAN2020 edition continues to take advantage of the relational structure and efficient interface available at www.hitran.org and the HITRAN Application Programming Interface (HAPI). The functionality of both tools has been extended for the new edition.

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  • 48. Gronoff, Guillaume
    et al.
    Maggiolo, Romain
    Cessateur, Gaël
    Moore, W. B.
    Airapetian, Vladimir
    De Keyser, Johan
    Dhooghe, Frederick
    Gibbons, Andrew
    Gunell, Herbert
    Royal Belgian Institute for Space Aeronomy(BIRA-IASB), Brussels, Belgium.
    Mertens, C. J.
    Rubin, Martin
    Hosseini, S.
    The Effect of Cosmic Rays on Cometary Nuclei. I. Dose Deposition2020In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 890, no 1, article id 89Article in journal (Refereed)
    Abstract [en]

    Comets are small bodies thought to contain the most pristine material in the solar system. However, since their formation ≈4.5 Gy ago, they have been altered by different processes. While not exposed to much electromagnetic radiation, they experience intense particle radiation. Galactic cosmic rays and solar energetic particles have a broad spectrum of energies and interact with the cometary surface and subsurface; they are the main source of space weathering for a comet in the Kuiper Belt or in the Oort Cloud, and also affect the ice prior to the comet agglomeration. While low-energy particles interact only with the cometary surface, the most energetic ones deposit a significant amount of energy down to tens of meters. This interaction can modify the isotopic ratios in cometary ices and create secondary compounds through radiolysis, such as O2 and H2O2 (Paper II). In this paper, we model the energy deposition of energetic particles as a function of depth using a Geant4 application modified to account for the isotope creation process. We quantify the energy deposited in cometary nucleus by galactic cosmic rays and solar energetic particles. The consequences of the energy deposition on the isotopic and chemical composition of cometary ices and their implication on the interpretation of cometary observations, notably of 67P/Churyumov Gerasimenko by the ESA Rosetta spacecraft, will be discussed in Paper II.

  • 49. Gunell, H
    et al.
    Andersson, L
    De Keyser, J
    Mann, Ingrid
    Umeå University, Faculty of Science and Technology, Department of Physics. EISCAT Scientific Association, Kiruna, Sweden.
    Self-consistent electrostatic simulations of reforming double layers in the downward current region of the aurora2015In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 33, no 10, p. 1331-1342Article in journal (Refereed)
    Abstract [en]

    The plasma on a magnetic field line in the downward current region of the aurora is simulated using a Vlasov model. It is found that an electric field parallel to the magnetic fields is supported by a double layer moving toward higher altitude. The double layer accelerates electrons upward, and these electrons give rise to plasma waves and electron phase-space holes through beam-plasma interaction. The double layer is disrupted when reaching altitudes of 12 Earth radii where the Langmuir condition no longer can be satisfied due to the diminishing density of electrons coming up from the ionosphere. During the disruption the potential drop is in part carried by the electron holes. The disruption creates favourable conditions for double layer formation near the ionosphere and double layers form anew in that region. The process repeats itself with a period of approximately 1 min. This period is determined by how far the double layer can reach before being disrupted: a higher disruption altitude corresponds to a longer repetition period. The disruption altitude is, in turn, found to increase with ionospheric density and to decrease with total voltage. The current displays oscillations around a mean value. The period of the oscillations is the same as the recurrence period of the double layer formations. The oscillation amplitude increases with increasing voltage, whereas the mean value of the current is independent of voltage in the 100 to 800 V range covered by our simulations. Instead, the mean value of the current is determined by the electron density at the ionospheric boundary.

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  • 50. Gunell, H
    et al.
    Mann, Ingrid
    Umeå University, Faculty of Science and Technology, Department of Physics. Eiscat Scientific Association, Kiruna, Sweden.
    Wedlund, C Simon
    Kallio, E
    Alho, M
    Nilsson, H
    De Keyser, J
    Dhooghe, F
    Maggiolo, R
    Acceleration of ions and nano dust at a comet in the solar wind2015In: Planetary and Space Science, ISSN 0032-0633, E-ISSN 1873-5088, Vol. 119, p. 13-23Article in journal (Refereed)
    Abstract [en]

    A quasi-neutral hybrid simulation of the interaction of the solar wind with the atmosphere of a comet is used together with a test particle simulation of cometary ions and dust to compute trajectories and velocity distribution functions of charged particles, starting outside the diamagnetic cavity at 150 km cometocentric distance. The simulations are run with parameters suited to make predictions for comet 67P/Churyumov-Gerasimenko when it is at a heliocentric distance of 1.45 AU. It is found that the shape of the ion trajectories depends on the location of the source, and that a velocity distribution that is observed at a given point in space is influenced by the spatial structure of the source. Charged dust grains with radii in the 1-10 nm range are accelerated from the nucleus to a distance of 2.9 x 104 km in between 15 min and 2 h approximately. Dust particles smaller than 10 nm in radius are accelerated to speeds over 10 km/s.

1234 1 - 50 of 161
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