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| Titel |
Global auroral conductance distribution due to electron and proton precipitation from IMAGE-FUV observations |
| VerfasserIn |
V. Coumans, J.-C. Gérard, B. Hubert, M. Meurant, S. B. Mende |
| 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. 5 ; Nr. 22, no. 5 (2004-04-08), S.1595-1611 |
| Datensatznummer |
250014861
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| Publikation (Nr.) |
 copernicus.org/angeo-22-1595-2004.pdf |
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| Zusammenfassung |
The Far Ultraviolet (FUV) imaging system on board the IMAGE satellite
provides a global view of the north auroral region in three spectral
channels, including the SI12 camera sensitive to Doppler shifted
Lyman-α emission. FUV images are used to produce instantaneous maps
of electron mean energy and energy fluxes for precipitated protons and
electrons. We describe a method to calculate ionospheric Hall and Pedersen
conductivities induced by auroral proton and electron ionization based on a
model of interaction of auroral particles with the atmosphere. Different
assumptions on the energy spectral distribution for electrons and protons
are compared. Global maps of ionospheric conductances due to instantaneous
observation of precipitating protons are calculated. The contribution of
auroral protons in the total conductance induced by both types of auroral
particles is also evaluated and the importance of proton precipitation is
evaluated. This method is well adapted to analyze the time evolution of
ionospheric conductances due to precipitating particles over the auroral
region or in particular sectors. Results are illustrated with conductance
maps of the north polar region obtained during four periods with different
activity levels. It is found that the proton contribution to conductance is
relatively higher during quiet periods than during substorms. The proton
contribution is higher in the period before the onset and strongly decreases
during the expansion phase of substorms. During a substorm which occurred on
28 April 2001, a region of strong proton precipitation is observed with
SI12 around 14:00MLT at ~75° MLAT. Calculation of
conductances in this sector shows that neglecting the protons contribution
would produce a large error. We discuss possible effects of the proton
precipitation on electron precipitation in auroral arcs. The increase in the
ionospheric conductivity, induced by a former proton precipitation can reduce
the potential drop along field lines in the upward field-aligned currents by
creating an opposite polarization electric field. This feedback mechanism
possibly reduces the electron acceleration.
Key words. Ionosphere (auroral ionosphere; ionospheremagnetosphere
interactions; particle precipitation) |
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