Investigating the anatomy of magnetosheath jets - MMS observations
File(s)angeo-36-655-2018[1].pdf (8.22 MB)
Published version
Author(s)
Type
Journal Article
Abstract
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−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.
Date Issued
2018-04-23
Date Acceptance
2018-04-03
Citation
ANNALES GEOPHYSICAE, 2018, 36 (2), pp.655-677
ISSN
0992-7689
Publisher
COPERNICUS GESELLSCHAFT MBH
Start Page
655
End Page
677
Journal / Book Title
ANNALES GEOPHYSICAE
Volume
36
Issue
2
Copyright Statement
© 2018 Author(s). This work is distributed under
the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/).
the Creative Commons Attribution 4.0 License (https://creativecommons.org/licenses/by/4.0/).
Identifier
http://gateway.webofknowledge.com/gateway/Gateway.cgi?GWVersion=2&SrcApp=PARTNER_APP&SrcAuth=LinksAMR&KeyUT=WOS:000430718500001&DestLinkType=FullRecord&DestApp=ALL_WOS&UsrCustomerID=1ba7043ffcc86c417c072aa74d649202
Subjects
Science & Technology
Physical Sciences
Astronomy & Astrophysics
Geosciences, Multidisciplinary
Meteorology & Atmospheric Sciences
Geology
Magnetospheric physics
magnetosheath
plasma waves and instabilities
solar wind-magnetosphere interactions
EARTHS BOW SHOCK
HIGH-SPEED JETS
SOLAR-WIND
MAGNETOSPHERIC MULTISCALE
TANGENTIAL DISCONTINUITY
SUBSOLAR MAGNETOSHEATH
CLUSTER OBSERVATIONS
PRESSURE PULSES
UPSTREAM WAVES
ENERGETIC IONS
Publication Status
Published
Date Publish Online
2018-04-23