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| Titel |
Ion temperature anisotropy and related plasma instabilities in the near-Earth magnetotail |
| VerfasserIn |
B. Zieger, A. Retinò, R. Nakamura |
| Konferenz |
EGU General Assembly 2012
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 14 (2012) |
| Datensatznummer |
250066940
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| Zusammenfassung |
| The interaction between fast reconnection outflow jets and the ambient plasma sheet in the
near-Earth flow-braking region often results in significant ion temperature anisotropy. In this
paper, we present CLUSTER case studies of ion temperature anisotropy around multiple
dipolarization fronts. Usually, large parallel anisotropy (Tpar > Tperp) is observed inside
fast jets or bursty bulk flows (BBFs), confirming the bubble model of BBFs. However,
significant perpendicular anisotropy (Tpar < Tperp) is found in the ambient high-β plasma
ahead of and between multiple dipolarization fronts. The perpendicular anisotropy is
most probably produced by adiabatic betatron acceleration through the magnetic
pileup process. If the mirror instability threshold is surpassed within the pileup
region, mirror mode structures are generated, which tend to remove the perpendicular
anisotropy by heating the trapped ion population. Thus the kinetic energy of the fast jet
is partly transformed into thermal energy. The mirror mode structures reported
in corotating ineraction regions (CIRs) in the solar wind must be produced by a
similar mechanism. Finally, we show a CLUSTER example where the non-linear
steepening of a mirror wave resulted in a kinetic shocklet within the pileup region
ahead of a jet front, leading to more efficient non-adiabatic particle acceleration. |
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