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| Titel |
Electron cross talk and asymmetric electron distributions near the Earth's bowshock |
| VerfasserIn |
J. J. Mitchell, S. J. Schwartz, U. Auster |
| Medientyp |
Artikel
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| Sprache |
Englisch
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| ISSN |
0992-7689
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| Digitales Dokument |
URL |
| Erschienen |
In: Annales Geophysicae ; 30, no. 3 ; Nr. 30, no. 3 (2012-03-06), S.503-513 |
| Datensatznummer |
250017196
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| Publikation (Nr.) |
 copernicus.org/angeo-30-503-2012.pdf |
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| Zusammenfassung |
| Electron distributions in the magnetosheath display a number of far from
equilibrium features. It has been suggested that one factor influencing these
distributions may be the large distances separating locations at which electrons
with different energies and pitch angles must cross the bowshock in order to
reach a given point in the magnetosheath. The overall heating requirements at
these distant locations depends strongly on the shock geometry. In the absence
of collisions or other isotropization processes this suggests that the
convolution of electrons arriving from different locations should give rise to
asymmetries in the distribution functions. Moreover, such cross-talk could
influence the relative electron to ion heating, rendering the shock heating
problem intrinsically non-local in contrast to classic shock physics. Here, we
study electron distributions measured simultaneously by the Plasma Electron and
Current Experiment (PEACE) on board the Cluster spacecraft and the Electrostatic
Analyser (ESA) on board THEMIS b during a time interval in which both the
Cluster spacecraft and THEMIS b are in the magnetosheath, close to the bowshock,
and during which the local magnetic field orientation makes it likely that
electron trajectories may connect both spacecraft. We find that the relevant
portions of the velocity distributions of such electrons measured by each
spacecraft display remarkable similarities. We map trajectories of electrons
arriving at each spacecraft back to the locations at which they crossed the
bowshock, as a function of pitch angle and energy. We then use the
Rankine-Hugoniot relations to estimate the heating of electrons and compare this
with temperature asymmetries actually observed. We conclude that the electron
distributions and temperatures in the magnetosheath depend heavily on non-local
shock properties. |
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