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Alm, L., Farrugia, C. J., Paulson, K. W., Argall, M. R., Torbert, R. B., Burch, J. L., . . . Giles, B. L. (2018). Differing Properties of Two Ion-Scale Magnetopause Flux Ropes. Journal of Geophysical Research - Space Physics, 123(1), 114-131
Open this publication in new window or tab >>Differing Properties of Two Ion-Scale Magnetopause Flux Ropes
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2018 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 1, p. 114-131Article in journal (Refereed) Published
Abstract [en]

In this paper, we present results from the Magnetospheric Multiscale constellation encountering two ion-scale, magnetopause flux ropes. The two flux ropes exhibit very different properties and internal structure. In the first flux rope, there are large differences in the currents observed by different satellites, indicating variations occurring over sub-d(i) spatial scales, and time scales on the order of the ion gyroperiod. In addition, there is intense wave activity and particle energization. The interface between the two flux ropes exhibits oblique whistler wave activity. In contrast, the second flux rope is mostly quiescent, exhibiting little activity throughout the encounter. Changes in the magnetic topology and field line connectivity suggest that we are observing flux rope coalescence.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2018
National Category
Geophysics
Identifiers
urn:nbn:se:kth:diva-224066 (URN)10.1002/2017JA024525 (DOI)000425637600010 ()2-s2.0-85042272503 (Scopus ID)
Note

QC 20180314

Available from: 2018-03-14 Created: 2018-03-14 Last updated: 2018-03-14Bibliographically approved
Karlsson, T., Plaschke, F., Hietala, H., Archer, M., Blanco-Cano, X., Kajdic, P., . . . Gershman, D. J. (2018). Investigating the anatomy of magnetosheath jets - MMS observations. Annales Geophysicae, 36(2), 655-677
Open this publication in new window or tab >>Investigating the anatomy of magnetosheath jets - MMS observations
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2018 (English)In: Annales Geophysicae, ISSN 0992-7689, E-ISSN 1432-0576, Vol. 36, no 2, p. 655-677Article in journal (Refereed) Published
Abstract [en]

We use Magnetosphere Multiscale (MMS) mission data to investigate a small number of magnetosheath jets, which are localized and transient increases in dynamic pressure, typically due to a combined increase in plasma velocity and density. For two approximately hour-long intervals in November, 2015 we found six jets, which are of two distinct types. (a) Two of the jets are associated with the magnetic field discontinuities at the boundary between the quasi-parallel and quasi-perpendicular magnetosheath. Straddling the boundary, the leading part of these jets contains an ion population similar to the quasi-parallel magnetosheath, while the trailing part contains ion populations similar to the quasi-perpendicular magnetosheath. Both populations are, however, cooler than the surrounding ion populations. These two jets also have clear increases in plasma density and magnetic field strength, correlated with a velocity increase. (b) Three of the jets are found embedded within the quasi-parallel magnetosheath. They contain ion populations similar to the surrounding quasi-parallel magnetosheath, but with a lower temperature. Out of these three jets, two have a simple structure. For these two jets, the increases in density and magnetic field strength are correlated with the dynamic pressure increases. The other jet has a more complicated structure, and no clear correlations between density, magnetic field strength and dynamic pressure. This jet has likely interacted with the magnetosphere, and contains ions similar to the jets inside the quasi-parallel magnetosheath, but shows signs of adiabatic heating. All jets are associated with emissions of whistler, lower hybrid, and broadband electrostatic waves, as well as approximately 10 s period electromagnetic waves with a compressional component. The latter have a Poynting flux of up to 40 mu Wm(-2) and may be energetically important for the evolution of the jets, depending on the wave excitation mechanism. Only one of the jets is likely to have modified the surrounding magnetic field into a stretched configuration, as has recently been reported in other studies. None of the jets are associated with clear signatures of either magnetic or thermal pressure gradient forces acting on them. The different properties of the two types also point to different generation mechanisms, which are discussed here. Their different properties and origins suggest that the two types of jets need to be separated in future statistical and simulation studies.

Place, publisher, year, edition, pages
COPERNICUS GESELLSCHAFT MBH, 2018
Keywords
Magnetospheric physics, magnetosheath, plasma waves and instabilities, solar wind-magnetosphere interactions
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-227770 (URN)10.5194/angeo-36-655-2018 (DOI)000430718500001 ()2-s2.0-85045938787 (Scopus ID)
Funder
Knut and Alice Wallenberg Foundation, KAW2012.0078Swedish Research Council, 2014-4694
Note

QC 20180514

Available from: 2018-05-14 Created: 2018-05-14 Last updated: 2018-05-14Bibliographically approved
Zhou, M., Berchem, J., Walker, R. J., El-Alaoui, M., Goldstein, M. L., Lapenta, G., . . . Marklund, G. (2018). Magnetospheric Multiscale Observations of an Ion Diffusion Region With Large Guide Field at the Magnetopause: Current System, Electron Heating, and Plasma Waves. Journal of Geophysical Research - Space Physics, 123(3), 1834-1852
Open this publication in new window or tab >>Magnetospheric Multiscale Observations of an Ion Diffusion Region With Large Guide Field at the Magnetopause: Current System, Electron Heating, and Plasma Waves
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2018 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 123, no 3, p. 1834-1852Article in journal (Refereed) Published
Abstract [en]

We report Magnetospheric Multiscale (MMS) observations of a reconnecting current sheet in the presence of a weak density asymmetry with large guide field at the dayside magnetopause. An ion diffusion region (IDR) was detected associated with this current sheet. Parallel current dominated over the perpendicular current in the IDR, as found in previous studies of component reconnection. Electrons were preferentially heated parallel to the magnetic field within the IDR. The heating was manifested as a flattop distribution below 400eV. Two types of electromagnetic electron whistler waves were observed within the regions where electrons were heated. One type of whistler wave was associated with nonlinear structures in E-|| with amplitudes up to 20mV/m. The other type was not associated with any structures in E-||. Poynting fluxes of these two types of whistler waves were directed away from the X-line. We suggest that the nonlinear evolution of the oblique whistler waves gave rise to the solitary structures in E-||. There was a perpendicular super-Alfvenic outflow jet that was carried by magnetized electrons. Intense electrostatic lower hybrid drift waves were localized in the current sheet center and were probably driven by the super-Alfvenic electron jet, the velocity of which was approximately equal to the diamagnetic drift of demagnetized ions. Our observations suggest that the guide field significantly modified the structures (Hall electromagnetic fields and current system) and wave properties in the IDR.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2018
Keywords
magnetic reconnection, dayside magnetopause, ion diffusion region, guide field, plasma waves
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-227237 (URN)10.1002/2017JA024517 (DOI)000430125300011 ()2-s2.0-85045517221 (Scopus ID)
Note

QC 20180518

Available from: 2018-05-18 Created: 2018-05-18 Last updated: 2018-05-18Bibliographically approved
Zhou, M., Berchem, J., Walker, R. J., El-Alaoui, M., Deng, X., Cazzola, E., . . . Burch, J. L. (2017). Coalescence of Macroscopic Flux Ropes at the Subsolar Magnetopause: Magnetospheric Multiscale Observations. Physical Review Letters, 119(5), Article ID 055101.
Open this publication in new window or tab >>Coalescence of Macroscopic Flux Ropes at the Subsolar Magnetopause: Magnetospheric Multiscale Observations
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2017 (English)In: Physical Review Letters, ISSN 0031-9007, E-ISSN 1079-7114, Vol. 119, no 5, article id 055101Article in journal (Refereed) Published
Abstract [en]

We report unambiguous in situ observation of the coalescence of macroscopic flux ropes by the magnetospheric multiscale (MMS) mission. Two coalescing flux ropes with sizes of similar to 1 R-E were identified at the subsolar magnetopause by the occurrence of an asymmetric quadrupolar signature in the normal component of the magnetic field measured by the MMS spacecraft. An electron diffusion region (EDR) with a width of four local electron inertial lengths was embedded within the merging current sheet. The EDR was characterized by an intense parallel electric field, significant energy dissipation, and suprathermal electrons. Although the electrons were organized by a large guide field, the small observed electron pressure nongyrotropy may be sufficient to support a significant fraction of the parallel electric field within the EDR. Since the flux ropes are observed in the exhaust region, we suggest that secondary EDRs are formed further downstream of the primary reconnection line between the magnetosheath and magnetospheric fields.

Place, publisher, year, edition, pages
American Physical Society, 2017
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-212332 (URN)10.1103/PhysRevLett.119.055101 (DOI)000406760300013 ()2-s2.0-85026918290 (Scopus ID)
Note

QC 20170821

Available from: 2017-08-21 Created: 2017-08-21 Last updated: 2017-11-10Bibliographically approved
Alm, L., Argall, M. R., Torbert, R. B., Farrugia, C. J., Burch, J. L., Ergun, R. E., . . . Shuster, J. (2017). EDR signatures observed by MMS in the 16 October event presented in a 2-D parametric space. Journal of Geophysical Research - Space Physics, 122(3), 3262-3276
Open this publication in new window or tab >>EDR signatures observed by MMS in the 16 October event presented in a 2-D parametric space
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2017 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 3, p. 3262-3276Article in journal (Refereed) Published
Abstract [en]

We present a method for mapping the position of satellites relative to the X line using the measured B-L and B-N components of the magnetic field and apply it to the Magnetospheric multiscale (MMS) encounter with the electron diffusion region (EDR) which occurred on 13:07 UT on 16 October 2015. Mapping the data to our parametric space succeeds in capturing many of the signatures associated with magnetic reconnection and the electron diffusion region. This offers a method for determining where in the reconnection region the satellites were located. In addition, parametric mapping can also be used to present data from numerical simulations. This facilitates comparing data from simulations with data from in situ observations as one can avoid the complicated process using boundary motion analysis to determine the geometry of the reconnection region. In parametric space we can identify the EDR based on the collocation of several reconnection signatures, such as electron nongyrotropy, electron demagnetization, parallel electric fields, and energy dissipation. The EDR extends 2-3km in the normal direction and in excess of 20km in the tangential direction. It is clear that the EDR occurs on the magnetospheric side of the topological X line, which is expected in asymmetric reconnection. Furthermore, we can observe a north-south asymmetry, where the EDR occurs north of the peak in out-of-plane current, which may be due to the small but finite guide field.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2017
Keywords
magnetic reconnection, electron diffusion region, MMS, parametric space, multispacecraft, asymmetric reconnection
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-206707 (URN)10.1002/2016JA023788 (DOI)000399710900030 ()2-s2.0-85016392229 (Scopus ID)
Note

QC 20170508

Available from: 2017-05-08 Created: 2017-05-08 Last updated: 2017-05-08Bibliographically approved
Chasapis, A., Matthaeus, W. H., Parashar, T. N., Lecontel, O., Retinò, A., Breuillard, H., . . . Saito, Y. (2017). Electron Heating at Kinetic Scales in Magnetosheath Turbulence. Astrophysical Journal, 836(2), Article ID 247.
Open this publication in new window or tab >>Electron Heating at Kinetic Scales in Magnetosheath Turbulence
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2017 (English)In: Astrophysical Journal, ISSN 0004-637X, E-ISSN 1538-4357, Vol. 836, no 2, article id 247Article in journal (Refereed) Published
Abstract [en]

We present a statistical study of coherent structures at kinetic scales, using data from the Magnetospheric Multiscale mission in the Earth's magnetosheath. We implemented the multi-spacecraft partial variance of increments (PVI) technique to detect these structures, which are associated with intermittency at kinetic scales. We examine the properties of the electron heating occurring within such structures. We find that, statistically, structures with a high PVI index are regions of significant electron heating. We also focus on one such structure, a current sheet, which shows some signatures consistent with magnetic reconnection. Strong parallel electron heating coincides with whistler emissions at the edges of the current sheet.

Place, publisher, year, edition, pages
Institute of Physics Publishing (IOPP), 2017
Keywords
acceleration of particles, magnetic reconnection, plasmas, turbulence
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-208005 (URN)10.3847/1538-4357/836/2/247 (DOI)000401169200015 ()2-s2.0-85014247266 (Scopus ID)
Note

QC 2017-06-08

Available from: 2017-06-08 Created: 2017-06-08 Last updated: 2017-06-13Bibliographically approved
Graham, D. B., Khotyaintsev, Y. V. V., Norgren, C., Vaivads, A., Andre, M., Toledo-Redondo, S., . . . Burch, J. L. (2017). Lower hybrid waves in the ion diffusion and magnetospheric inflow regions. Journal of Geophysical Research - Space Physics, 122(1), 517-533
Open this publication in new window or tab >>Lower hybrid waves in the ion diffusion and magnetospheric inflow regions
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2017 (English)In: Journal of Geophysical Research - Space Physics, ISSN 2169-9380, E-ISSN 2169-9402, Vol. 122, no 1, p. 517-533Article in journal (Refereed) Published
Abstract [en]

The role and properties of lower hybrid waves in the ion diffusion region and magnetospheric inflow region of asymmetric reconnection are investigated using the Magnetospheric Multiscale (MMS) mission. Two distinct groups of lower hybrid waves are observed in the ion diffusion region and magnetospheric inflow region, which have distinct properties and propagate in opposite directions along the magnetopause. One group develops near the ion edge in the magnetospheric inflow, where magnetosheath ions enter the magnetosphere through the finite gyroradius effect and are driven by the ion-ion cross-field instability due to the interaction between the magnetosheath ions and cold magnetospheric ions. This leads to heating of the cold magnetospheric ions. The second group develops at the sharpest density gradient, where the Hall electric field is observed and is driven by the lower hybrid drift instability. These drift waves produce cross-field particle diffusion, enabling magnetosheath electrons to enter the magnetospheric inflow region thereby broadening the density gradient in the ion diffusion region.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2017
Keywords
Magnetic reconnection, Ion diffusion region, Lower hybrid waves
National Category
Fusion, Plasma and Space Physics
Identifiers
urn:nbn:se:kth:diva-205170 (URN)10.1002/2016JA023572 (DOI)000395655800038 ()2-s2.0-85010693276 (Scopus ID)
Note

QC 20170411

Available from: 2017-04-11 Created: 2017-04-11 Last updated: 2017-11-29Bibliographically approved
Voros, Z., Yordanova, E., Varsani, A., Genestreti, K. J., Khotyaintsev, Y. V. V., Li, W., . . . Saito, Y. (2017). MMS Observation of Magnetic Reconnection in the Turbulent Magnetosheath. Journal of Geophysical Research - Space Physics, 122(11), 11442-11467
Open this publication in new window or tab >>MMS Observation of Magnetic Reconnection in the Turbulent Magnetosheath
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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. 11442-11467Article in journal (Refereed) Published
Abstract [en]

In this paper we use the full armament of the MMS (Magnetospheric Multiscale) spacecraft to study magnetic reconnection in the turbulent magnetosheath downstream of a quasi-parallel bow shock. Contrarily to the magnetopause and magnetotail cases, only a few observations of reconnection in the magnetosheath have been reported. The case study in this paper presents, for the first time, both fluid-scale and kinetic-scale signatures of an ongoing reconnection in the turbulent magnetosheath. The spacecraft are crossing the reconnection inflow and outflow regions and the ion diffusion region (IDR). Inside the reconnection outflows D shape ion distributions are observed. Inside the IDR mixing of ion populations, crescent-like velocity distributions and ion accelerations are observed. One of the spacecraft skims the outer region of the electron diffusion region, where parallel electric fields, energy dissipation/conversion, electron pressure tensor agyrotropy, electron temperature anisotropy, and electron accelerations are observed. Some of the difficulties of the observations of magnetic reconnection in turbulent plasma are also outlined.

Place, publisher, year, edition, pages
AMER GEOPHYSICAL UNION, 2017
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-221889 (URN)10.1002/2017JA024535 (DOI)000419938600034 ()2-s2.0-85038393392 (Scopus ID)
Note

QC 20180131

Available from: 2018-01-31 Created: 2018-01-31 Last updated: 2018-01-31Bibliographically approved
Matsui, H., Erickson, P. J., Foster, J. C., Torbert, R. B., Argall, M. R., Anderson, B. J., . . . Turner, D. L. (2016). Dipolarization in the inner magnetosphere during a geomagnetic storm on 7 October 2015. Geophysical Research Letters, 43(18), 9397-9405
Open this publication in new window or tab >>Dipolarization in the inner magnetosphere during a geomagnetic storm on 7 October 2015
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2016 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 18, p. 9397-9405Article in journal (Refereed) Published
Abstract [en]

A dipolarization event was observed by the Magnetospheric Multiscale (MMS) spacecraft at L = 3.8 and 19.8 magnetic local time starting at similar to 23:42:36 UT on 7 October 2015. The magnetic and electric fields showed initially coherent variations between the spacecraft. The sunward convection turned tailward after the dipolarization. The observation is interpreted in terms of the pressure balance or the momentum equation. This was followed by a region traversed where the fields were irregular. The scale length was of the order of the ion gyroradius, suggesting the kinetic nature of the fluctuations. Combination of the multi-instrument, multispacecraft data reveals a more detailed picture of the dipolarization event in the inner magnetosphere. Conjunction ionosphere-plasmasphere observations from DMSP, two-dimensional GPS total electron content, the Millstone Hill midlatitude incoherent scatter radar, and AMPERE measurements imply that MMS observations are located on the poleward edge of the ionospheric trough where Region 2 field-aligned currents flow.

Place, publisher, year, edition, pages
American Geophysical Union (AGU), 2016
National Category
Geosciences, Multidisciplinary
Identifiers
urn:nbn:se:kth:diva-196421 (URN)10.1002/2016GL070677 (DOI)000385392900006 ()2-s2.0-84988640811 (Scopus ID)
Note

QC 20161128

Available from: 2016-11-28 Created: 2016-11-14 Last updated: 2017-11-29Bibliographically approved
Wilder, F. D., Ergun, R. E., Schwartz, S. J., Newman, D. L., Eriksson, S., Stawarz, J. E., . . . Magnes, W. (2016). Observations of large-amplitude, parallel, electrostatic waves associated with the Kelvin-Helmholtz instability by the magnetospheric multiscale mission. Geophysical Research Letters, 43(17), 8859-8866
Open this publication in new window or tab >>Observations of large-amplitude, parallel, electrostatic waves associated with the Kelvin-Helmholtz instability by the magnetospheric multiscale mission
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2016 (English)In: Geophysical Research Letters, ISSN 0094-8276, E-ISSN 1944-8007, Vol. 43, no 17, p. 8859-8866Article in journal (Refereed) Published
Abstract [en]

On 8 September 2015, the four Magnetospheric Multiscale spacecraft encountered a Kelvin-Helmholtz unstable magnetopause near the dusk flank. The spacecraft observed periodic compressed current sheets, between which the plasma was turbulent. We present observations of large-amplitude (up to 100 mV/m) oscillations in the electric field. Because these oscillations are purely parallel to the background magnetic field, electrostatic, and below the ion plasma frequency, they are likely to be ion acoustic-like waves. These waves are observed in a turbulent plasma where multiple particle populations are intermittently mixed, including cold electrons with energies less than 10 eV. Stability analysis suggests a cold electron component is necessary for wave growth.

Place, publisher, year, edition, pages
Blackwell Publishing, 2016
Keywords
boundary layer, electrostatic waves, Kelvin-Helmholtz, turbulence, Boundary layers, Electric field effects, Electric fields, Electrostatics, Magnetosphere, Plasma turbulence, Spacecraft, Ion plasma frequency, Kelvin- helmholtz instabilities, Magnetospheric multi scale, Magnetospheric multiscale missions, Multiple particles, Stability analysis, Atmospheric thermodynamics, amplitude, electric field, Kelvin-Helmholtz instability, magnetic field, magnetopause, observational method, plasma
National Category
Physical Sciences
Identifiers
urn:nbn:se:kth:diva-195326 (URN)10.1002/2016GL070404 (DOI)2-s2.0-84984837657 (Scopus ID)
Note

QC 20161109

Available from: 2016-11-09 Created: 2016-11-02 Last updated: 2017-11-29Bibliographically approved
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Identifiers
ORCID iD: ORCID iD iconorcid.org/0000-0002-1594-1861

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