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| Titel |
Effects of energetic electrons on the electrodynamics in the ionosphere |
| VerfasserIn |
A. Aksnes, J. Stadsnes, G. Lu, N. Østgaard, R. R. Vondrak, D. L. Detrick, T. J. Rosenberg, G. A. Germany, M. Schulz |
| 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 ; 22, no. 2 ; Nr. 22, no. 2 (2004-01-01), S.475-496 |
| Datensatznummer |
250014777
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| Publikation (Nr.) |
 copernicus.org/angeo-22-475-2004.pdf |
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| Zusammenfassung |
From the observations by the PIXIE and UVI cameras on board the
Polar satellite, we derive global maps of the precipitating
electron energy spectra from less than 1keV to 100keV. Based on
the electron spectra, we generate instantaneous global maps of
Hall and Pedersen conductances. The UVI camera provides good
coverage of the lower electron energies contributing most to the
Pedersen conductance, while PIXIE captures the high energy
component of the precipitating electrons affecting the Hall
conductance. By characterizing the energetic electrons from some
tens of keV and up to about 100keV using PIXIE X-ray
measurements, we will, in most cases, calculate a larger electron
flux at higher energies than estimated from a simple extrapolation
of derived electron spectra from UVI alone. Instantaneous global
conductance maps derived with and without inclusion of PIXIE data
have been implemented in the Assimilative Mapping of Ionospheric
Electrodynamics (AMIE) procedure, to study the effects of energetic
electrons on electrodynamical parameters in the ionosphere. We
find that the improved electron spectral characterization using
PIXIE data most often results in a larger Hall conductance and a
smaller inferred electric field. In some localized regions the
increase in the Hall conductance can exceed 100%. On the
contrary, the Pedersen conductance remains more or less unaffected
by the inclusion of the PIXIE data. The calculated polar cap
potential drop may decrease more than 10%, resulting in a
reduction of the estimated Joule heating integrated over the
Northern Hemisphere by up to 20%. Locally, Joule heating
may decrease more than 50% in some regions. We also find
that the calculated energy flux by precipitating electrons
increases around 5% when including the PIXIE data. Combined
with the reduction of Joule heating, this results in a decrease in
the ratio between Joule heating and energy flux, sometimes
exceeding 25%. An investigation of the relationship between
Joule heating and the AE index shows a nearly linear
correspondence between the two quantities, in accordance with
previous studies. However, we find lower proportionality factors
than reported by others when taking geomagnetic conditions into
account, ranging between 0.13 and 0.23GW/nT. We also find that
the contribution from auroral particles to the energy budget is
more important than most previous studies have reported.
Key words. Ionosphere (auroral ionosphere; particle precipitation)
– Magnetospheric physics (storms and substorms) |
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