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| Titel |
High-latitude electromagnetic and particle energy flux during an event with sustained strongly northward IMF |
| VerfasserIn |
H. Korth, B. J. Anderson, H. U. Frey, C. L. Waters |
| 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 ; 23, no. 4 ; Nr. 23, no. 4 (2005-06-03), S.1295-1310 |
| Datensatznummer |
250015224
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1295-2005.pdf |
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| Zusammenfassung |
| We present a case study of a prolonged interval of strongly
northward orientation of the interplanetary magnetic field on 16 July
2000, 16:00-19:00 UT to characterize the energy exchange
between the magnetosphere and ionosphere for conditions associated
with minimum solar wind-magnetosphere coupling. With reconnection
occurring tailward of the cusp under northward IMF conditions, the
reconnection dynamo should be separated from the viscous dynamo,
presumably driven by the Kelvin-Helmholtz (KH) instability. Thus,
these conditions are also ideal for evaluating the contribution of
a viscous interaction to the coupling process. We derive the
two-dimensional distribution of the Poynting vector radial
component in the northern sunlit polar ionosphere from magnetic
field observations by the constellation of Iridium satellites
together with drift meter and magnetometer observations from the
Defense Meteorological Satellite Program (DMSP) F13 and F15
satellites. The electromagnetic energy flux is then compared with
the particle energy flux obtained from auroral images taken by the
far-ultraviolet (FUV) instrument on the Imager for Magnetopause to
Aurora Global Exploration (IMAGE) spacecraft. The electromagnetic
energy input to the ionosphere of 51 GW calculated from the
Iridium/DMSP observations is eight times larger than the 6 GW due
to particle precipitation all poleward of 78° MLAT. This
result indicates that the energy transport is significant,
particularly as it is concentrated in a small region near the
magnetic pole, even under conditions traditionally considered to
be quiet and is dominated by the electromagnetic flux. We estimate
the contributions of the high and mid-latitude dynamos to both the
Birkeland currents and electric potentials finding that
high-latitude reconnection accounts for 0.8 MA and 45kV while we
attribute <0.2MA and ~5kV to an interaction at lower
latitudes having the sense of a viscous interaction. Given that
these conditions are ideal for the occurrence of the KH
instability at the magnetopause and hence the viscous interaction,
this result suggests that the viscous interaction is a small
contributor to coupling solar wind energy to the
magnetosphere-ionosphere system. |
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