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Liu, T., Pitkänen, T., Nilsson, S., Kullen, A., Park, J.-S., Hamrin, M., . . . Yao, S. (2025). IMF By influence on fast earthward convection flows in the near-lunar magnetotail. Geoscience Letters, 12(1), Article ID 6.
Open this publication in new window or tab >>IMF By influence on fast earthward convection flows in the near-lunar magnetotail
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2025 (English)In: Geoscience Letters, E-ISSN 2196-4092, Vol. 12, no 1, article id 6Article in journal (Refereed) Published
Abstract [en]

This study investigates the effects of non-zero IMF By on the magnetotail By and fast earthward ion convection (V⊥ > 200 km/s, "⊥" indicates perpendicular to the magnetic field) in the near-lunar magnetotail plasma sheet using the plasma parameters and magnetic field detected by the ARTEMIS (Acceleration, Reconnection, Turbulence, and Electrodynamics of the Moon’s Interaction with the Sun) P1 satellite during the period 2011–2022. We find that the magnetotail By with in the same direction as IMF By dominates the entire region. The IMF By influence is hemisphere-independent, but shows a dusk-dawn asymmetry with the IMF By effect being weaker in the premidnight region than in the postmidnight region. We also find that the IMF By influence on earthward fast convection results in an interhemispheric flow asymmetry and it is highly correlated with the direction of magnetotail By. The statistical results indicate that occasionally localized dynamics can have a significant effect on magnetotail By and V⊥.

Place, publisher, year, edition, pages
Springer Nature, 2025
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-236199 (URN)10.1186/s40562-025-00379-5 (DOI)001416326700001 ()2-s2.0-85218493500 (Scopus ID)
Available from: 2025-03-17 Created: 2025-03-17 Last updated: 2025-03-17Bibliographically approved
Krämer, E., Hamrin, M., Gunell, H., Baddeley, L., Partamies, N., Raptis, S., . . . Schillings, A. (2025). Magnetosheath jet-triggered ULF waves: energy deposition in the ionosphere. Journal of Geophysical Research - Space Physics, 130(4), Article ID e2025JA033792.
Open this publication in new window or tab >>Magnetosheath jet-triggered ULF waves: energy deposition in the ionosphere
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2025 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 130, no 4, article id e2025JA033792Article in journal (Refereed) Published
Abstract [en]

Magnetosheath jets, transient plasma structures of enhanced dynamic pressure, have been observed to trigger ultra-low frequency (ULF) waves in the magnetosphere. These ULF waves contribute to energy transport in the magnetosphere-ionosphere system. Therefore, there is a need to estimate the energy input into the ionosphere due to jet-triggered ULF waves. In this study, we combine measurements from Magnetospheric Multiscale, ground-based magnetometers, the EISCAT radar on Svalbard, and SuperDARN to estimate the Joule heating in the ionosphere resulting from jet impacts at the magnetopause. Focusing on three jets observed on 2016-01-07 we were able to calculate the Joule heating for two jets. We found an average Joule heating rate of (Formula presented.) mW/m2 which is on par with other processes such as field line resonances. However, due to the short duration and spatial confinement of the jet-induced ULF waves, the average energy input was only (Formula presented.) J. This suggests that the energy deposition of jet-triggered ULF waves is small compared to other magnetospheric processes, and thus does not significantly impact the average energy budget of the magnetosphere.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2025
Keywords
joule heating, magnetosheath jets, ULF waves
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-239179 (URN)10.1029/2025JA033792 (DOI)001469888700001 ()2-s2.0-105005413452 (Scopus ID)
Funder
Swedish Research Council, 2018‐03623Swedish National Space Board, 2022‐00138Swedish National Space Board, 2023‐00208The Research Council of Norway, 343302Swedish Research Council, 2021‐06683
Available from: 2025-06-13 Created: 2025-06-13 Last updated: 2025-06-13Bibliographically approved
Yao, S., Zhang, H., Shi, Q., Liu, J., Guo, R., Sun, W., . . . Tian, A. (2024). Electron vortex generation in earth's collisionless bow shock: MMS observations. Journal of Geophysical Research - Space Physics, 129(9), Article ID e2024JA032980.
Open this publication in new window or tab >>Electron vortex generation in earth's collisionless bow shock: MMS observations
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2024 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 129, no 9, article id e2024JA032980Article in journal (Refereed) Published
Abstract [en]

In astrophysics and space, supercritical shock is generated when an object interacts with an incoming supersonic plasma stream. Its downstream plasmas are highly turbulent, containing abundant vortices on all scales from magnetohydrodynamic to electron gyroscales. Understanding the production of these vortices is at the forefront, especially on the electron scale. Using ultrafast measurements of NASA's Magnetospheric Multiscale spacecraft, we report on the fortunate multi-spacecraft observation of the formation of an electron vortex directly generated inside the Earth's quasi-parallel bow shock transition and propagated to the downstream turbulent magnetosheath. The vortex is generated inside the shock transition by anisotropic ∼100–600 eV electrons trapped in an ion-scale magnetic hole which could show a tornado-like magnetic morphology. Our results demonstrate that the electron vortex can develop not only as a product of the forward cascade but also from the shock transition into its downstream turbulence, which adds to the short-scale turbulence and dissipation.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2024
Keywords
collisionless shock, electron vortex, magnetic hole, magnetosheath, mms, turbulence
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-230162 (URN)10.1029/2024JA032980 (DOI)001316162100001 ()2-s2.0-85204681651 (Scopus ID)
Available from: 2024-10-02 Created: 2024-10-02 Last updated: 2024-10-02Bibliographically approved
Shi, Q., Yao, S., Hamrin, M. & Liu, J. (2024). Kinetic scale magnetic holes in the terrestrial magnetosheath: a review. Science China. Earth Sciences, 67(9), 2739-2771
Open this publication in new window or tab >>Kinetic scale magnetic holes in the terrestrial magnetosheath: a review
2024 (English)In: Science China. Earth Sciences, ISSN 1674-7313, E-ISSN 1869-1897, Vol. 67, no 9, p. 2739-2771Article, review/survey (Refereed) Published
Abstract [en]

Magnetic holes at the ion-to-electron kinetic scale (KSMHs) are one of the extremely small intermittent structures generated in turbulent magnetized plasmas. In recent years, the explorations of KSMHs have made substantial strides, driven by the ultra-high-precision observational data gathered from the Magnetospheric Multiscale (MMS) mission. This review paper summarizes the up-to-date characteristics of the KSMHs observed in Earth’s turbulent magnetosheath, as well as their potential impacts on space plasma. This review starts by introducing the fundamental properties of the KSMHs, including observational features, particle behaviors, scales, geometries, and distributions in terrestrial space. Researchers have discovered that KSMHs display a quasi-circular electron vortex-like structure attributed to electron diamagnetic drift. These electrons exhibit noticeable non-gyrotropy and undergo acceleration. The occurrence rate of KSMH in the Earth’s magnetosheath is significantly greater than in the solar wind and magnetotail, suggesting the turbulent magnetosheath is a primary source region. Additionally, KSMHs have also been generated in turbulence simulations and successfully reproduced by the kinetic equilibrium models. Furthermore, KSMHs have demonstrated their ability to accelerate electrons by a novel non-adiabatic electron acceleration mechanism, serve as an additional avenue for energy dissipation during magnetic reconnection, and generate diverse wave phenomena, including whistler waves, electrostatic solitary waves, and electron cyclotron waves in space plasma. These results highlight the magnetic hole’s impact such as wave-particle interaction, energy cascade/dissipation, and particle acceleration/heating in space plasma. We end this paper by summarizing these discoveries, discussing the generation mechanism, similar structures, and observations in the Earth’s magnetotail and solar wind, and presenting a future extension perspective in this active field.

Place, publisher, year, edition, pages
Springer Nature, 2024
Keywords
Coherent structure, Electron acceleration, Electron vortex, Kinetic scale, Magnetic dip/cavity, Magnetic hole, Magnetosheath, Mirror mode, Turbulence, Whistler
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-228289 (URN)10.1007/s11430-023-1290-8 (DOI)001282852600003 ()2-s2.0-85200164557 (Scopus ID)
Available from: 2024-08-08 Created: 2024-08-08 Last updated: 2024-08-20Bibliographically approved
Fatemi, S., Hamrin, M., Krämer, E., Gunell, H., Nordin, G., Karlsson, T. & Goncharov, O. (2024). Unveiling the 3D structure of magnetosheath jets. Monthly notices of the Royal Astronomical Society, 531(4), 4692-4713
Open this publication in new window or tab >>Unveiling the 3D structure of magnetosheath jets
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2024 (English)In: Monthly notices of the Royal Astronomical Society, ISSN 0035-8711, E-ISSN 1365-2966, Vol. 531, no 4, p. 4692-4713Article in journal (Refereed) Published
Abstract [en]

Magnetosheath jets represent localized enhancements in dynamic pressure observed within the magnetosheath. These energetic entities, carrying excess energy and momentum, can impact the magnetopause and disrupt the magnetosphere. Therefore, they play a vital role in coupling the solar wind and terrestrial magnetosphere. However, our understanding of the morphology and formation of these complex, transient events remains incomplete over two decades after their initial observation. Previous studies have relied on oversimplified assumptions, considering jets as elongated cylinders with dimensions ranging from $0.1\, R_{\rm E}$ to $5\, R_{\rm E}$ (Earth radii). In this study, we present simulation results obtained from Amitis, a high-performance hybrid-kinetic plasma framework (particle ions and fluid electrons) running in parallel on graphics processing units (GPUs) for fast and more environmentally friendly computation compared to CPU-based models. Considering realistic scales, we present the first global, three-dimensional (3D in both configuration and velocity spaces) hybrid-kinetic simulation results of the interaction between solar wind plasma and the Earth. Our high-resolution kinetic simulations reveal the 3D structure of magnetosheath jets, showing that jets are far from being simple cylinders. Instead, they exhibit intricate and highly interconnected structures with dynamic 3D characteristics. As they move through the magnetosheath, they wrinkle, fold, merge, and split in complex ways before a subset reaches the magnetopause.

Place, publisher, year, edition, pages
Oxford University Press, 2024
Keywords
planet stars, interactionlanet star, numerical, planets and satellites, terrestrial planets, planets and satellites, magnetic fields, plasmas
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:umu:diva-228720 (URN)10.1093/mnras/stae1456 (DOI)001253786600002 ()
Funder
Swedish National Space Board, 2022-00138Swedish National Space Board, 115/18Swedish Research Council, 2018-03454Swedish Research Council, 2018-03623
Available from: 2024-08-22 Created: 2024-08-22 Last updated: 2024-08-22Bibliographically approved
Östman, S., Gunell, H., Hamrin, M., Opgenoorth, H. J. & Andersson, L. (2024). Width of the quasi-perpendicular bow shock region at Mars. Astronomy and Astrophysics, 689, Article ID A110.
Open this publication in new window or tab >>Width of the quasi-perpendicular bow shock region at Mars
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2024 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 689, article id A110Article in journal (Refereed) Published
Abstract [en]

Aims: We aim to quantify the width of the quasi-perpendicular Martian bow shock region to deepen the understanding of why the width is variable and which factors affect it, and to explore the implications on thermalization.

Methods: To quantify the width, 2074 quasi-perpendicular bow shock crossings from a database were studied. Upstream conditions, such as Mach numbers, dynamic pressure, ion densities, and other factors, were considered. Furthermore, the difference between the downstream and upstream temperature was measured.

Results: We found that the shock region width is correlated with the magnetosonic Mach number, the critical ratio, and the overshoot amplitude. The region was found to be anticorrelated with dynamic pressure. The width is not affected by the upstream ion density of the investigated species or by the upstream temperature. The difference between the downstream and upstream temperature is not affected by the shock region width.

Conclusions: We found that the factors that affect the stand-off distance of the bow shock, such as the magnetosonic Mach number and dynamic pressure, also affect the width. The width is also positively correlated with the overshoot amplitude, indicating that the structures are coupled or that they are affected by largely the same conditions. The lack of a correlation with the ion temperature difference indicates that the shock region width does not affect the ion thermalization.

Place, publisher, year, edition, pages
EDP Sciences, 2024
Keywords
plasmas, shock waves, methods: data analysis, planets and satellites: terrestrial planets, planet-star interactions, planets and satellites: individual: Mars
National Category
Fusion, Plasma and Space Physics Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:umu:diva-232436 (URN)10.1051/0004-6361/202348385 (DOI)001308055500028 ()2-s2.0-85215438924 (Scopus ID)
Funder
Swedish National Space Board, 108/18Swedish National Space Board, 194/19
Available from: 2024-11-29 Created: 2024-11-29 Last updated: 2025-01-31Bibliographically approved
Dredger, P. M., Lopez, R. E. & Hamrin, M. (2023). A case study in support of closure of bow shock current through the ionosphere utilizing multi-point observations and simulation. Frontiers in Astronomy and Space Sciences, 10, Article ID 1098388.
Open this publication in new window or tab >>A case study in support of closure of bow shock current through the ionosphere utilizing multi-point observations and simulation
2023 (English)In: Frontiers in Astronomy and Space Sciences, E-ISSN 2296-987X, Vol. 10, article id 1098388Article in journal (Refereed) Published
Abstract [en]

On the bow shock in front of Earth's magnetosphere flows a current due to the curl of the interplanetary magnetic field across the shock. The closure of this current remains uncertain; it is unknown whether the bow shock current closes with the Chapman-Ferraro current system on the magnetopause, along magnetic field lines into the ionosphere, through the magnetosheath, or some combination thereof. We present simultaneous observations from Magnetosphere Multiscale (MMS), AMPERE, and Defense Meteorological Satellite Program (DMSP) during a period of strong By, weakly negative Bz, and very small Bx. This IMF orientation should lead to a bow shock current flowing mostly south to north on the shock. AMPERE shows a current poleward of the Region 1 and Region 2 Birkeland currents flowing into the northern polar cap and out of the south, the correct polarity for bow shock current to be closing along open field lines. A southern Defense Meteorological Satellite Program F18 flyover confirms that this current is poleward of the convection reversal boundary. Additionally, we investigate the bow shock current closure for the above-mentioned solar wind conditions using an MHD simulation of the event. We compare the magnitude of the modeled bow shock current due to the IMF By component to the magnitude of the modeled high-latitude current that corresponds to the real current observed in AMPERE and by Defense Meteorological Satellite Program. In the simulation, the current poleward of the Region 1 currents is about 37% as large as the bow shock Iz in the northern ionosphere and 60% in the south. We conclude that the evidence points to at least a partial closure of the bow shock current through the ionosphere.

Place, publisher, year, edition, pages
Frontiers Media S.A., 2023
Keywords
bow shock current, closure, DMSP, FAC, LFM, MMS
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-205365 (URN)10.3389/fspas.2023.1098388 (DOI)000933640300001 ()2-s2.0-85148374902 (Scopus ID)
Funder
Swedish Research Council
Available from: 2023-03-29 Created: 2023-03-29 Last updated: 2023-03-29Bibliographically approved
Pitkänen, T., Chong, G. S., Hamrin, M., Kullen, A., Vanhamäki, H., Park, J.-S., . . . Krämer, E. (2023). Fast Earthward Convection in the Magnetotail and Nonzero IMF By: MMS Statistics. Journal of Geophysical Research - Space Physics, 128(12), Article ID e2023JA031593.
Open this publication in new window or tab >>Fast Earthward Convection in the Magnetotail and Nonzero IMF By: MMS Statistics
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2023 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 128, no 12, article id e2023JA031593Article in journal (Refereed) Published
Abstract [en]

We statistically investigate convective earthward fast flows using data measured by the Magnetospheric Multiscale mission in the tail plasma sheet during 2017–2021. We focus on “frozen in” fast flows and investigate the importance of different electric field components in the Sun-Earth (V⊥x) and dusk-dawn (V⊥y) velocity components perpendicular to the magnetic field. We find that a majority of the fast flow events (52% of 429) have the north-south electric field component (Ez) as the most relevant or dominating component whereas 26% are so-called conventional type fast flows with Ey and Ex as the relevant components. The rest of the flow events, 22%, fall into the two ’mixed’ categories, of which almost all these fast flows, 20% of 429, have Ey and Ez important for V⊥x and V⊥y, respectively. There is no Y-location preference for any type of the fast flows. The conventional fast flows are detected rather close to the neutral sheet whereas the other types can be measured farther away. Typical total speeds are highest in the mixed category. Typical perpendicular speeds are comparably high in the conventional and mixed categories. The slowest fast flows are measured in the Ez category. Most of the fast flow events are measured in the substorm recovery phase. Prevailing interplanetary magnetic field By conditions influence the V⊥y direction and the influence is most efficient for the Ez-dominated fast flows.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2023
National Category
Fusion, Plasma and Space Physics Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:umu:diva-218880 (URN)10.1029/2023JA031593 (DOI)001130317300001 ()2-s2.0-85180501515 (Scopus ID)
Funder
Swedish National Space Board, 118/17Swedish National Space Board, 271/14Swedish National Space Board, 194/19Swedish National Space Board, 81/17Swedish Research Council, 2018-03623Swedish Research Council, 2021-06683Academy of Finland, 354521
Available from: 2024-01-04 Created: 2024-01-04 Last updated: 2025-04-24Bibliographically approved
Yao, S., Li, J., Zhou, X.-Z., Shi, Q., Zong, Q.-G., Zhang, H., . . . Yang, F. (2023). Ion-Vortex Magnetic Hole With Reversed Field Direction in Earth's Magnetosheath. Journal of Geophysical Research - Space Physics, 128(7), Article ID e2023JA031749.
Open this publication in new window or tab >>Ion-Vortex Magnetic Hole With Reversed Field Direction in Earth's Magnetosheath
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2023 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 128, no 7, article id e2023JA031749Article in journal (Refereed) Published
Abstract [en]

Plasma vortices are ubiquitous in space and play important roles in the transmission of energy and mass at various scales. For small-scale plasma vortices on the order of ion gyroradius, however, their properties and characteristics remain unclear. Here, we provide unique findings of an ion-scale vortex observed in the Earth's magnetosheath. The vortex is generated by the ion diamagnetic drift associated with an isolated magnetic hole (MH). The magnetic field in the axial direction is reversed in the vortex center, which is consistent with ring-shaped currents carried by the ions. The field strength becomes very weak (<1 nT) at the field reversal region, although the ion distributions vary rather continuously across the entire structure. A kinetic equilibrium model is then applied to reconstruct the above features. These findings can help us understand the plasma vortex and MH from magnetohydrodynamics to kinetic scales.

Place, publisher, year, edition, pages
John Wiley & Sons, 2023
Keywords
electron vortex, ion vortex, kinetic scale, magnetic hole, magnetosheath
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-212504 (URN)10.1029/2023JA031749 (DOI)001040706400001 ()2-s2.0-85165598754 (Scopus ID)
Available from: 2023-08-01 Created: 2023-08-01 Last updated: 2025-04-24Bibliographically approved
Gunell, H., Hamrin, M., Nesbit-Östman, S., Krämer, E. & Nilsson, H. (2023). Magnetosheath jets at Mars. Science Advances, 9(22), Article ID eadg5703.
Open this publication in new window or tab >>Magnetosheath jets at Mars
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2023 (English)In: Science Advances, E-ISSN 2375-2548, Vol. 9, no 22, article id eadg5703Article in journal (Refereed) Published
Abstract [en]

Plasma entities, known as magnetosheath jets, with higher dynamic pressure than the surrounding plasma, are often seen at Earth. They generate waves and contribute to energy transfer in the magnetosheath. Affecting the magnetopause, they cause surface waves and transfer energy into the magnetosphere, causing throat auroras and magnetic signatures detectable on the ground. We show that jets exist also beyond Earth's environment in the magnetosheath of Mars, using data obtained by the MAVEN spacecraft. Thus, jets can be created also at Mars, which differs from Earth by its smaller bow shock, and they are associated with an increased level of magnetic field fluctuations. Jets couple large and small scales in magnetosheaths in the solar system and can play a similar part in astrophysical plasmas.

Place, publisher, year, edition, pages
American Association for the Advancement of Science (AAAS), 2023
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-209550 (URN)10.1126/sciadv.adg5703 (DOI)001009737900017 ()37267367 (PubMedID)2-s2.0-85160904545 (Scopus ID)
Funder
Swedish National Space Board, 108/18Swedish National Space Board, 194/19Swedish Research Council, 2018-03623
Available from: 2023-06-13 Created: 2023-06-13 Last updated: 2023-09-05Bibliographically approved
Projects
Energy and mass transfer related to bursty bulk flows [78/11_SNSB]; Umeå UniversityThe interplay between plasma flows and magnetic fields in Earth's magnetotail - A PhD project on the importance of instabilities [105/14_SNSB]; Umeå UniversityThe interplay between plasma flows and magnetic fields in Earth's magnetotail - A PhD project on the importance of instabilities [271/14_SNSB]; Umeå UniversityProlongation of postdoc position for Timo Pitkänen: Energy and mass transfer related to bursty bulk flows [77/14 P_SNSB]; Umeå UniversityWave-particle interactions in the complex environment of a comet [201/15_SNSB]; Umeå UniversityGeoeffectiveness of bow shock processes [2018-03623_VR]; Umeå University
Organisations
Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-2043-4442

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