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| Titel |
Oxygen ion energization by waves in the high altitude cusp and mantle |
| VerfasserIn |
M. Waara, H. Nilsson, R. Slapak, M. André, G. Stenberg |
| 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. 9 ; Nr. 30, no. 9 (2012-09-03), S.1309-1314 |
| Datensatznummer |
250017263
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| Publikation (Nr.) |
 copernicus.org/angeo-30-1309-2012.pdf |
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| Zusammenfassung |
| We present a comparative study of low frequency electric field spectral
densities and temperatures observed by the Cluster spacecraft in the high
altitude cusp/mantle region. We compare the relation between the O+
temperature and wave intensity at the oxygen gyrofrequency at each
measurement point and find a clear correlation. The trend of the correlation
agrees with the predictions by both an asymptotic mean-particle theory and a
test-particle approach. The perpendicular to parallel temperature ratio is
also consistent with the predictions of the asymptotic mean-particle theory.
At times the perpendicular temperature is significantly higher than predicted
by the models. A simple study of the evolution of the particle distributions
(conics) at these altitudes indicates that enhanced perpendicular
temperatures would be observed over many RE after heating ceases.
Therefore, sporadic intense heating is the likely explanation for cases with
high temperature and comparably low wave activity. We observe waves of
sufficient amplitude to explain the highest observed temperatures, while the
theory in general overestimates the temperature associated with the highest
observed wave activity, indicating that such high wave activity is very
sporadic. |
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