Investigating the anatomy of magnetosheath jets – MMS observations
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...
| Main Authors: | , , , , , , , , |
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| Format: | Article |
| Language: | English |
| Published: |
Copernicus Publications
2018-04-01
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| Series: | Annales Geophysicae |
| Online Access: | https://www.ann-geophys.net/36/655/2018/angeo-36-655-2018.pdf |
| _version_ | 1818348902400655360 |
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| author | T. Karlsson F. Plaschke H. Hietala M. Archer X. Blanco-Cano P. Kajdič P.-A. Lindqvist G. Marklund D. J. Gershman |
| author_facet | T. Karlsson F. Plaschke H. Hietala M. Archer X. Blanco-Cano P. Kajdič P.-A. Lindqvist G. Marklund D. J. Gershman |
| author_sort | T. Karlsson |
| collection | DOAJ |
| description | 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 µW m<sup>−2</sup> 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. |
| first_indexed | 2024-12-13T17:57:26Z |
| format | Article |
| id | doaj.art-81f59ee936004d34ac4f5b105feac6e5 |
| institution | Directory Open Access Journal |
| issn | 0992-7689 1432-0576 |
| language | English |
| last_indexed | 2024-12-13T17:57:26Z |
| publishDate | 2018-04-01 |
| publisher | Copernicus Publications |
| record_format | Article |
| series | Annales Geophysicae |
| spelling | doaj.art-81f59ee936004d34ac4f5b105feac6e52022-12-21T23:36:20ZengCopernicus PublicationsAnnales Geophysicae0992-76891432-05762018-04-013665567710.5194/angeo-36-655-2018Investigating the anatomy of magnetosheath jets – MMS observationsT. Karlsson0F. Plaschke1H. Hietala2M. Archer3X. Blanco-Cano4P. Kajdič5P.-A. Lindqvist6G. Marklund7D. J. Gershman8Space and Plasma Physics, School of Electrical Engineering, KTH Royal Institute of Technology, 100 44 Stockholm, SwedenSpace Research Institute, Austrian Academy of Sciences, Schmiedlstrasse 6, 8042 Graz, AustriaDepartment of Earth, Planetary, and Space Sciences, University of California Los Angeles, 603 Charles E. Young Drive East, Slichter Hall 6844D, Los Angeles, CA 90095-1567, USASchool of Physics & Astronomy, Queen Mary University of London, London, E1 4NS, UKInstituto de Geofísica Universidad Nacional Autónoma de México, Ciudad Universitaria, CDMX, MéxicoInstituto de Geofísica Universidad Nacional Autónoma de México, Ciudad Universitaria, CDMX, MéxicoSpace and Plasma Physics, School of Electrical Engineering, KTH Royal Institute of Technology, 100 44 Stockholm, SwedenSpace and Plasma Physics, School of Electrical Engineering, KTH Royal Institute of Technology, 100 44 Stockholm, SwedenNASA Goddard Space Flight Center, Greenbelt, Maryland, USAWe 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 µW m<sup>−2</sup> 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.https://www.ann-geophys.net/36/655/2018/angeo-36-655-2018.pdf |
| spellingShingle | T. Karlsson F. Plaschke H. Hietala M. Archer X. Blanco-Cano P. Kajdič P.-A. Lindqvist G. Marklund D. J. Gershman Investigating the anatomy of magnetosheath jets – MMS observations Annales Geophysicae |
| title | Investigating the anatomy of magnetosheath jets – MMS observations |
| title_full | Investigating the anatomy of magnetosheath jets – MMS observations |
| title_fullStr | Investigating the anatomy of magnetosheath jets – MMS observations |
| title_full_unstemmed | Investigating the anatomy of magnetosheath jets – MMS observations |
| title_short | Investigating the anatomy of magnetosheath jets – MMS observations |
| title_sort | investigating the anatomy of magnetosheath jets ndash mms observations |
| url | https://www.ann-geophys.net/36/655/2018/angeo-36-655-2018.pdf |
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