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De Spiegeleer, A., Hamrin, M., Gunell, H., Volwerk, M., Andersson, L., Karlsson, T., . . . Kistler, L. M. (2019). Oscillatory Flows in the Magnetotail Plasma Sheet: Cluster Observations of the Distribution Function. Journal of Geophysical Research - Space Physics, 124(4), 2736-2754
Open this publication in new window or tab >>Oscillatory Flows in the Magnetotail Plasma Sheet: Cluster Observations of the Distribution Function
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2019 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 124, no 4, p. 2736-2754Article in journal (Refereed) Published
Abstract [en]

Plasma dynamics in Earth's magnetotail is often studied using moments of the distribution function, which results in losing information on the kinetic properties of the plasma. To better understand oscillatory flows observed in the midtail plasma sheet, we investigate two events, one in each hemisphere, in the transition region between the central plasma sheet and the lobes using the 2-D ion distribution function from the Cluster 4 spacecraft. In this case study, the oscillatory flows are a manifestation of repeated ion flux enhancements with pitch angle changing from 0 degrees to 180 degrees in the Northern Hemisphere and from 180 degrees to 0 degrees in the Southern Hemisphere. Similar pitch angle signatures are observed seven times in about 80 min for the Southern Hemisphere event and three times in about 80 min for the Northern Hemisphere event. The ion flux enhancements observed for both events are slightly shifted in time between different energy channels, indicating a possible time-of-flight effect from which we estimate that the source of particle is located similar to 5-25R(E) and similar to 40-107R(E) tailward of the spacecraft for the Southern and Northern Hemisphere event, respectively. Using a test particle simulation, we obtain similar to 21-46 R-E for the Southern Hemisphere event and tailward of X similar to - 65R(E) (outside the validity region of the model) for the Northern Hemisphere event. We discuss possible sources that could cause the enhancements of ion flux.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2019
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-162349 (URN)10.1029/2018JA026116 (DOI)000477707800027 ()
Available from: 2019-08-27 Created: 2019-08-27 Last updated: 2019-08-27Bibliographically approved
Pitkänen, T., Kullen, A., Shi, Q. Q., Hamrin, M., De Spiegeleer, A. & Nishimura, Y. (2018). Convection electric field and plasma convection in a twisted magnetotail: t THEMIS case study 1-2 January 2009. Journal of Geophysical Research - Space Physics, 123(9), 7486-7497
Open this publication in new window or tab >>Convection electric field and plasma convection in a twisted magnetotail: t THEMIS case study 1-2 January 2009
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2018 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 9, p. 7486-7497Article in journal (Refereed) Published
Abstract [en]

We investigate THEMIS satellite measurements made in a tail-aligned constellation during a time interval on 1-2 January 2009, which has previously been attributed to an interval of an interplanetary magnetic fieldB(y)-driven magnetotail twisting. We find evidence for that the orientation of the convection electric field in the tail is twist-mode dependent. For earthward flow and a negative twist (induced tail B-y < 0), the electric field is found to have northward E-z and tailward E-x components. During a positive twist (induced tail B-y > 0), the directions of E-z and E-x are reversed. The E-y component shows the expected dawn-to-dusk direction for earthward flow. The electric field components preserve their orientation across the neutral sheet, and a quasi-collinear field is observed irrespective to the tail distance. The electric field associated with the tailward flow has an opposite direction compared to the earthward flow for the negative twist. For the positive twist, the results are less clear. The corresponding plasma convection and thus the magnetic flux transport have an opposite dawn-dusk direction above and below the neutral sheet. The directions depend on the tail twist mode. The hemispherically asymmetric earthward plasma flows are suggested to be a manifestation of an asymmetric Dungey cycle in a twisted magnetotail. The role of tailward flows deserve further investigation.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2018
National Category
Fusion, Plasma and Space Physics Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:umu:diva-153821 (URN)10.1029/2018JA025688 (DOI)000448376600025 ()
Available from: 2018-12-11 Created: 2018-12-11 Last updated: 2018-12-11Bibliographically approved
Lindkvist, J., Hamrin, M., Gunell, H., Nilsson, H., Simon Wedlund, C., Kallio, E., . . . Karlsson, T. (2018). Energy conversion in cometary atmospheres: Hybrid modeling of 67P/Churyumov-Gerasimenko. Astronomy and Astrophysics, 616, Article ID A81.
Open this publication in new window or tab >>Energy conversion in cometary atmospheres: Hybrid modeling of 67P/Churyumov-Gerasimenko
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2018 (English)In: Astronomy and Astrophysics, ISSN 0004-6361, E-ISSN 1432-0746, Vol. 616, article id A81Article in journal (Refereed) Published
Abstract [en]

Aims. We wish to investigate the energy conversion between particles and electromagnetic fields and determine the location where it occurs in the plasma environment of comets.

Methods. We used a hybrid plasma model that included photoionization, and we considered two cases of the solar extreme ultraviolet flux. Other parameters corresponded to the conditions of comet 67P/Churyumov-Gerasimenko at a heliocentric distance of 1.5 AU.

Results. We find that a shock-like structure is formed upstream of the comet and acts as an electromagnetic generator, similar to the bow shock at Earth that slows down the solar wind. The Poynting flux transports electromagnetic energy toward the inner coma, where newly born cometary ions are accelerated. Upstream of the shock-like structure, we find local energy transfer from solar wind ions to cometary ions. We show that mass loading can be a local process with a direct transfer of energy, but also part of a dynamo system with electromagnetic generators and loads.

Conclusions. The energization of cometary ions is governed by a dynamo system for weak ionization, but changes into a large conversion region with local transfer of energy directly from solar wind protons for high ionization.

Place, publisher, year, edition, pages
EDP Sciences, 2018
Keywords
comets: individual: 67P/Churyumov-Gerasimenko, Sun: UV radiation, solar wind, methods: numerical, plasmas, acceleration of particles
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-148207 (URN)10.1051/0004-6361/201732353 (DOI)000442541100001 ()
Funder
Swedish National Space Board, 201/15Swedish National Space Board, 112/13Swedish Research Council, 2015-04187
Available from: 2018-05-30 Created: 2018-05-30 Last updated: 2018-09-10Bibliographically approved
Vaverka, J., Pellinen-Wannberg, A., Kero, J., Mann, I., De Spiegeleer, A., Hamrin, M., . . . Pitkänen, T. (2017). Detection of EMPs generated by meteoroid impacts on the MMS spacecraft and problems with signal interpretation. In: 2017 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS): . Paper presented at 32nd General Assembly and Scientific Symposium of the International-Union-of-Radio-Science (URSI GASS), Montreal, QC, Canada, 19-26 August, 2017. IEEE
Open this publication in new window or tab >>Detection of EMPs generated by meteoroid impacts on the MMS spacecraft and problems with signal interpretation
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2017 (English)In: 2017 XXXIInd General Assembly and Scientific Symposium of the International Union of Radio Science (URSI GASS), IEEE, 2017Conference paper, Published paper (Refereed)
Abstract [en]

Signatures of hypervelocity dust impacts detected by electric field instruments are still not completely understood. We have used the electric field instrument onboard one of the MMS spacecraft orbiting the Earth since 2015 to study various pulses in the measured electric field detected simultaneously by multiple antennas. This unique instrument allows a detailed investigation of registered waveforms. The preliminary results shown that the solitary waves can generate similar pulses as dust impacts and detected pulses can easily by misinterpreted when only one antenna is used.

Place, publisher, year, edition, pages
IEEE, 2017
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-163055 (URN)10.23919/URSIGASS.2017.8105218 (DOI)000463723600268 ()978-90-825987-0-4 (ISBN)
Conference
32nd General Assembly and Scientific Symposium of the International-Union-of-Radio-Science (URSI GASS), Montreal, QC, Canada, 19-26 August, 2017
Available from: 2019-09-09 Created: 2019-09-09 Last updated: 2019-09-09Bibliographically approved
Vaverka, J., Pellinen-Wannberg, A., Kero, J., Mann, I., De Spiegeleer, A., Hamrin, M., . . . Pitkänen, T. (2017). Detection of meteoroid hypervelocity impacts on the Cluster spacecraft: First results. Journal of Geophysical Research - Space Physics, 122(6), 6485-6494
Open this publication in new window or tab >>Detection of meteoroid hypervelocity impacts on the Cluster spacecraft: First results
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2017 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 6, p. 6485-6494Article in journal (Refereed) Published
Abstract [en]

We present the first study of dust impact events on one of the Earth-orbiting Cluster satellites. The events were identified in the measurements of the wide band data (WBD) instrument on board the satellite operating in monopole configuration. Since 2009 the instrument is operating in this configuration due to the loss of three electric probes and is therefore measuring the potential between the only operating antenna and the spacecraft body. Our study shows that the WBD instrument on Cluster 1 is able to detect pulses generated by dust impacts and discusses four such events. The presence of instrumental effects, intensive natural waves, noncontinuous sampling modes, and the automatic gain control complicates this detection. Due to all these features, we conclude that the Cluster spacecraft are not ideal for dust impact studies. We show that the duration and amplitudes of the pulses recorded by Cluster are similar to pulses detected by STEREO, and the shape of the pulses can be described with the model of the recollection of impact cloud electrons by the positively charged spacecraft. We estimate that the detected impacts were generated by micron-sized grains with velocities in the order of tens of km/s.

Keywords
hypervelocity impact, dust detection, interplanetary dust
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-138045 (URN)10.1002/2016JA023755 (DOI)000405534800040 ()
Available from: 2017-08-14 Created: 2017-08-14 Last updated: 2019-09-09Bibliographically approved
De Spiegeleer, A., Hamrin, M., Pitkänen, T., Volwerk, M., Mann, I., Nilsson, H., . . . Vaverka, J. (2017). Low-frequency oscillatory flow signatures and high-speed flows in the Earth's magnetotail. Journal of Geophysical Research - Space Physics, 122(7), 7042-7056
Open this publication in new window or tab >>Low-frequency oscillatory flow signatures and high-speed flows in the Earth's magnetotail
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2017 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 7, p. 7042-7056Article in journal (Refereed) Published
Abstract [en]

Using plasma sheet data from Cluster 1 spacecraft from 2001 till 2011, we statistically investigate oscillatory signatures in the plasma bulk flow. These periodic oscillations are compared to high-speed and quiet flows. Periodic oscillations are observed approximately 8% of the time, while high-speed flows and quiet flows are observed around 0.5% and 12% of the time, respectively. We remark that periodic oscillations can roughly occur everywhere for x(gsm) < -10 R-E and |y(gsm)| < 10 RE, while quiet flows mainly occur toward the flanks of this region and toward x = -10 R-E. The relation between the geomagnetic and solar activity and the occurrence of periodic oscillations is investigated and reveal that periodic oscillations occur for most Kp values and solar activity, while quiet flows are more common during low magnetospheric and solar activity. We find that the median oscillation frequency of periodic oscillations is 1.7 mHz and the median duration of the oscillation events is 41 min. We also observe that their associated Poynting vectors show a tendency to be earthward (S-x >= 0). Finally, the distribution of high-speed flows and periodic oscillations as a function of the velocity is investigated and reveals that thresholds lower than 200 km/s should not be used to identify high-speed flows as it could result in misinterpreting a periodic oscillations for a high-speed flow.

Place, publisher, year, edition, pages
Washington: American Geophysical Union (AGU), 2017
Keywords
bursty bulk flows, plasma sheet, cluster observations, magnetic field, neutral sheet, magnetosphere, dependence, midtail
National Category
Fluid Mechanics and Acoustics
Identifiers
urn:nbn:se:umu:diva-139015 (URN)10.1002/2017JA024076 (DOI)000407627100008 ()
Funder
Swedish National Space Board, 271/14
Available from: 2017-09-14 Created: 2017-09-14 Last updated: 2019-09-09Bibliographically approved
Yao, S., Wang, X. G., Shi, Q. Q., Pitkänen, T., Hamrin, M., Yao, Z. H., . . . Liu, J. (2017). Observations of kinetic-size magnetic holes in the magnetosheath. Journal of Geophysical Research - Space Physics, 122(2), 1990-2000
Open this publication in new window or tab >>Observations of kinetic-size magnetic holes in the magnetosheath
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2017 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 2, p. 1990-2000Article in journal (Refereed) Published
Abstract [en]

Magnetic holes (MHs), with a scale much greater than ρ(proton gyroradius), have been widely reported in various regions of space plasmas. On the other hand, kinetic-size magnetic holes (KSMHs), previously called small-size magnetic holes, with a scale of the order of magnitude of or less than ρi have only been reported in the Earth's magnetospheric plasma sheet. In this study, we report such KSMHs in the magnetosheath whereby we use measurements from the Magnetospheric Multiscale mission, which provides three-dimensional (3-D) particle distribution measurements with a resolution much higher than previous missions. The MHs have been observed in a scale of 10-20 ρe (electron gyroradii) and lasted 0.1-0.3 s. Distinctive electron dynamics features are observed, while no substantial deviations in ion data are seen. It is found that at the 90 degrees pitch angle, the flux of electrons with energy 34-66 eV decreased, while for electrons of energy 109-1024 eV increased inside the MHs. We also find the electron flow vortex perpendicular to the magnetic field, a feature self-consistent with the magnetic depression. Moreover, the calculated current density is mainly contributed by the electron diamagnetic drift, and the electron vortex flow is the diamagnetic drift flow. The electron magnetohydrodynamics soliton is considered as a possible generation mechanism for the KSMHs with the scale size of 10-20 ρe.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2017
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-133552 (URN)10.1002/2016JA023858 (DOI)000397022900038 ()
Note

Special Section: Magnetospheric Multiscale (MMS) mission results throughout the first primary mission phase

Available from: 2017-04-12 Created: 2017-04-12 Last updated: 2019-09-09Bibliographically approved
Pitkänen, T., Hamrin, M., Karlsson, T., Nilsson, H. & Kullen, A. (2017). On IMF By-induced dawn-dusk asymmetries in earthward convective fast flows (1sted.). In: Stein Haaland, Andrei Runov, Colin Forsyth (Ed.), Dawn-dusk asymmetries in planetary plasma environments: (pp. 95-106). American Geophysical Union (AGU)
Open this publication in new window or tab >>On IMF By-induced dawn-dusk asymmetries in earthward convective fast flows
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2017 (English)In: Dawn-dusk asymmetries in planetary plasma environments / [ed] Stein Haaland, Andrei Runov, Colin Forsyth, American Geophysical Union (AGU), 2017, 1st, p. 95-106Chapter in book (Refereed)
Abstract [en]

Studies of earthward plasma and magnetic field transport in the Earth’s magnetotail plasma sheet have shown that, on the average, Earthward ion flows in the premidnight and midnight sectors exhibit a duskward component while flows in the postmidnight sector are dawnward. The flow pattern is more pronounced for slower flows (<100 km/s) and alters gradually to a more symmetric one with respect to midnight for increasing flow speeds. However, recent ionospheric and magnetospheric studies have suggested that a nonzero By component in the interplanetary magnetic field (IMF) may significantly influence the earthward transport, creating previously unnoticed dawn‐dusk asymmetries between the hemispheres. In this article, we give a short overview of the present understanding of the topic, present new results, and briefly discuss the importance of the IMF By component for the Earthward transport processes in the magnetotail plasma sheet.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2017 Edition: 1st
Series
Geophysical Monograph Series ; 230
National Category
Fusion, Plasma and Space Physics
Research subject
Space Physics
Identifiers
urn:nbn:se:umu:diva-154303 (URN)978-1-119-21632-2 (ISBN)
Funder
Swedish National Space Board, 77/14
Available from: 2018-12-15 Created: 2018-12-15 Last updated: 2018-12-15
Vaverka, J., Pellinen-Wannberg, A., Kero, J., Mann, I., De Spiegeleer, A., Hamrin, M., . . . Pitkänen, T. (2017). Potential of Earth Orbiting Spacecraft Influenced by Meteoroid Hypervelocity Impacts. IEEE Transactions on Plasma Science, 45(8), 2048-2055
Open this publication in new window or tab >>Potential of Earth Orbiting Spacecraft Influenced by Meteoroid Hypervelocity Impacts
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2017 (English)In: IEEE Transactions on Plasma Science, ISSN 0093-3813, E-ISSN 1939-9375, Vol. 45, no 8, p. 2048-2055Article in journal (Refereed) Published
Abstract [en]

Detection of hypervelocity impacts on a spacecraft body using electric field instruments has been established as a new method for monitoring of dust grains in our solar system. Voyager, WIND, Cassini, and STEREO spacecraft have shown that this technique can be a complementary method to conventional dust detectors. This approach uses fast short time changes in the spacecraft potential generated by hypervelocity dust impacts, which can be detected by monopole electric field instruments as a pulse in the measured electric field. The shape and the duration of the pulse strongly depend on parameters of the ambient plasma environment. This fact is very important for Earth orbiting spacecraft crossing various regions of the Earth's magnetosphere where the concentration and the temperature of plasma particles change significantly. We present the numerical simulations of spacecraft charging focused on changes in the spacecraft potential generated by dust impacts in various locations of the Earth's magnetosphere. We show that identical dust impacts generate significantly larger pulses in regions with lower electron density. We discuss the influence of the photoelectron distribution for dust impact detections showing that a small amount of energetic photoelectrons significantly increases the potential of the spacecraft body and the pulse duration. We also show that the active spacecraft potential control (ASPOC) instrument onboard the cluster spacecraft strongly reduces the amplitude and the duration of the pulse resulting in difficulties of dust detection when ASPOC is ON. Simulation of dust impacts is compared with pulses detected by the Earth orbiting cluster spacecraft in the last part of Section III.

Keywords
Dust grains, hypervelocity impacts, meteoroids, spacecraft charging
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:umu:diva-140978 (URN)10.1109/TPS.2017.2676984 (DOI)000407374400031 ()
Funder
Swedish National Space Board, 110/14Swedish National Space Board, 77/14
Available from: 2017-11-01 Created: 2017-11-01 Last updated: 2018-06-09Bibliographically approved
Maggiolo, R., Hamrin, M., De Keyser, J., Pitkanen, T., Cessateur, G., Gunell, H. & Maes, L. (2017). The Delayed Time Response of Geomagnetic Activity to the Solar Wind. Journal of Geophysical Research - Space Physics, 122(11), 109-127
Open this publication in new window or tab >>The Delayed Time Response of Geomagnetic Activity to the Solar Wind
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2017 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 11, p. 109-127Article in journal (Refereed) Published
Abstract [en]

We investigate the lagged correlation between a selection of geomagnetic indices and solar wind parameters for a complete solar cycle, from 2000 to 2011. We first discuss the mathematical assumptions required for such a correlation analysis. The solar wind parameters and geomagnetic indices have inherent timescales that smooth the variations of the correlation coefficients with time lag. Furthermore, the solar wind structure associated with corotating interaction regions and coronal mass ejections, and the compression regions ahead of them, strongly impacts the lagged correlation analysis results. This work shows that such bias must be taken into account in a correct interpretation of correlations. We then evidence that the magnetospheric response time to solar wind parameters involves multiple timescales. The simultaneous and quick response of the PC and AE indices to solar wind dynamic pressure with a delay of similar to 5 min suggests that magnetospheric compression by solar wind can trigger substorm activity. We find that the PC and AE indices respond to interplanetary magnetic field (IMF) B-Z with a response time of respectively similar to 20 and similar to 35 min. The response of the SYM-H index takes longer (similar to 80 min) and is less sharp, SYM-H being statistically significantly correlated to the IMF B-Z observed up to more than similar to 10 h before. Our results suggest that the solar wind velocity's dominant impact on geomagnetic activity is caused by the compression regions at the interface of fast/slow solar wind regimes, which are very geo-effective as they are associated with high solar wind pressure and strong interplanetary magnetic field.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2017
National Category
Astronomy, Astrophysics and Cosmology
Identifiers
urn:nbn:se:umu:diva-144364 (URN)10.1002/2016JA023793 (DOI)000419938600015 ()
Available from: 2018-02-02 Created: 2018-02-02 Last updated: 2018-06-09Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-5681-0366

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