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| Titel |
Conjugate high-intensity energetic electron precipitation at high latitude |
| VerfasserIn |
T. Christensen, N. Østgaard, T. J. Rosenberg, D. L. Detrick, G. A. Germany, P. Stauning |
| 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 ; 21, no. 7 ; Nr. 21, no. 7, S.1443-1455 |
| Datensatznummer |
250014653
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| Publikation (Nr.) |
 copernicus.org/angeo-21-1443-2003.pdf |
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| Zusammenfassung |
On 6 August 1998 an
intense precipitation event occurring at high latitude in the evening sector
was observed by X-ray and far-ultraviolet imagers on board the Polar satellite
and by several ground-based instruments. The precipitation region was centred
at approximately 19:00 MLT at 74° MLAT (at an L-shell of about 13). The event
started at 22:59 UT and lasted about 10 minutes. It happened during the late
expansion phase of a substorm after two hours of strongly southward IMF.
Imaging riometers at geomagnetically conjugate sites recorded strong absorption
levels which exceeded 7 dB at 38 MHz in a transient and localized
intensification occurring within a poleward moving arc-like feature. The
temporal and spatial similarities between the recordings from the two conjugate
regions are remarkable. The arc-like precipitation region progressed poleward
with a velocity of 1.5 km/s. Ground magnetometers co-located with the imaging
riometers observed disturbances consistent with poleward moving westward
currents. In X-ray and riometer images which are sensitive only to energetic
electrons (above 5–10 keV) the event seems isolated, but in UV images the
event is seen to occur on the poleward edge of the rapidly poleward expanding
evening side aurora. The energy spectrum of precipitating electrons was subject
to a temporary hardening which peaked at a mean energy of about 20 keV when the
event was at its most intense at 23:02 UT. The event is likely to have been
caused by an accelerating mechanism at some height above the ionosphere or by
an earthward flow burst in the magnetotail, or possibly both.
Key words. Magnetospheric physics
(energetic particles, precipitating; storms and substorms;
magnetosphere-ionosphere interactions) |
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