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| Titel |
Anisotropic pitch angle distribution of ~100 keV microburst electrons in the loss cone: measurements from STSAT-1 |
| VerfasserIn |
J. J. Lee, G. K. Parks, E. Lee, B. T. Tsurutani, J. Hwang, K. S. Cho, K.-H. Kim, Y. D. Park, K. W. Min, M. P. McCarthy |
| 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. 11 ; Nr. 30, no. 11 (2012-11-06), S.1567-1573 |
| Datensatznummer |
250017284
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| Publikation (Nr.) |
 copernicus.org/angeo-30-1567-2012.pdf |
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| Zusammenfassung |
| Electron microburst energy spectra in the range of 170 keV
to 360 keV have been measured using two solid-state detectors onboard
the low-altitude (680 km), polar-orbiting Korean STSAT-1 (Science and
Technology SATellite-1). Applying a unique capability of the spacecraft
attitude control system, microburst energy spectra have been accurately
resolved into two components: perpendicular to and parallel to the
geomagnetic field direction. The former measures trapped electrons and the
latter those electrons with pitch angles in the loss cone and precipitating
into atmosphere. It is found that the perpendicular component energy spectra
are harder than the parallel component and the loss cone is not completely
filled by the electrons in the energy range of 170 keV to 360 keV. These
results have been modeled assuming a wave-particle cyclotron resonance
mechanism, where higher energy electrons travelling within a magnetic
flux tube interact with whistler mode waves at higher latitudes (lower
altitudes). Our results suggest that because higher energy (relativistic)
microbursts do not fill the loss cone completely, only a small portion of
electrons is able to reach low altitude (~100 km) atmosphere. Thus
assuming that low energy microbursts and relativistic microbursts are
created by cyclotron resonance with chorus elements (but at different
locations), the low energy portion of the microburst spectrum will dominate
at low altitudes. This explains why relativistic microbursts have not been
observed by balloon experiments, which typically float at altitudes of ~30 km
and measure only X-ray flux produced by collisions between neutral
atmospheric particles and precipitating electrons. |
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