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| Titel |
Collisionless shocks in the solar corona: a mechanism for preferential heating of heavy ions |
| VerfasserIn |
Gaetano Zimbardo, Giuseppe Nistico' |
| Konferenz |
EGU General Assembly 2011
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| Medientyp |
Artikel
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| Sprache |
Englisch
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| Digitales Dokument |
PDF |
| Erschienen |
In: GRA - Volume 13 (2011) |
| Datensatznummer |
250053333
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| Zusammenfassung |
| The heating of the solar corona to temperatures of the order of 106 K and more is one of the
fundamental problems of solar physics. Beside the high temperatures, Soho/UVCS
observations have shown that heavy ions in polar corona, like O5+ and Mg9+, are heated
more than protons, and that heavy ion heating is more than mass proportional; further, the
perpendicular temperatures are much larger than parallel temperatures. Here, we
propose that the more than mass proportional heating of heavy ions in coronal holes
is due to the ion reflection at supercritical quasi-perpendicular shocks and to the
ion acceleration by the V Ã B electric field in the shock frame. The acceleration
due to motional electric field is perpendicular to the magnetic field, in agreement
with Soho/UVCS observations, and is more than mass proportional with respect to
protons, because the heavy ion orbit is mostly upstream of the quasi-perpendicular
shock foot. We discuss the mechanism of heavy ion reflection, which is based on
ion gyration in the magnetic overshoot of the shock. We also discuss the recent
determination of the full set of physical parameters for a fast mode shock observed in the
solar corona, which shows how the proposed mechanism could work. Further, we
present preliminary numerical simulations of the heavy ion reflection at collisionless
shocks. |
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