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| Titel |
New model for auroral acceleration: O-shaped potential structure cooperating with waves |
| VerfasserIn |
P. Janhunen  , A. Olsson |
| 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 ; 18, no. 6 ; Nr. 18, no. 6, S.596-607 |
| Datensatznummer |
250014015
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| Publikation (Nr.) |
 copernicus.org/angeo-18-596-2000.pdf |
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| Zusammenfassung |
There are recent observational indications
(lack of convergent electric field signatures above the auroral oval at 4 RE
altitude) that the U-shaped potential drop model for auroral acceleration is not
applicable in all cases. There is nevertheless much observational evidence
favouring the U-shaped model at low altitudes, i.e., in the acceleration region
and below. To resolve the puzzle we propose that there is a negative O-shaped
potential well which is maintained by plasma waves pushing the electrons into
the loss cone and up an electron potential energy hill at ~3-4RE
altitude range. We present a test particle simulation which shows that when the
wave energization is modelled by random parallel boosts, introducing an O-shaped
potential increases the precipitating energy flux because the electrons can stay
in the resonant velocity range for a longer time if a downward electric field
decelerates the electrons at the same time when waves accelerate them in the
parallel direction. The lower part of the O-shaped potential well is essentially
the same as in the U-shaped model. The electron energization comes from plasma
waves in this model, but the final low-altitude fluxes are produced by
electrostatic acceleration. Thus, the transfer of energy from waves to particles
takes places in an "energization region", which is above the
acceleration region. In the energization region the static electric field points
downward while in the acceleration region it points upward. The model is
compatible with the large body of low-altitude observations supporting the
U-shaped model while explaining the new observations of the lack of electric
field at high altitude.
Key words: Ionosphere (ionosphere-magnetosphere
interactions; particle acceleration) - Magnetospheric physics (auroral
phenomena) |
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