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| Titel |
Modeling of occurrence frequencies of ion conics as a function of altitude and conic angle |
| VerfasserIn |
W. Miyake, T. Mukai, N. Kaya |
| 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. 1 ; Nr. 18, no. 1, S.47-55 |
| Datensatznummer |
250013880
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| Publikation (Nr.) |
 copernicus.org/angeo-18-47-2000.pdf |
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| Zusammenfassung |
The occurrence frequencies of dayside ion
conics with various conic angles are obtained as a function of altitude from
Exos-D (Akebono) observations. We made a model calculation of ion conic
evolution to match the observation results. The observed occurrence frequencies
of ion conics with 80° to 90° conic
angle are used as an input to the model and the occurrence frequencies of ion
conics with smaller conic angles are numerically calculated at higher altitudes.
The calculated occurrence frequencies are compared with the observed ones of ion
conics with smaller conic angles. We take into account conic angle variation
with altitude in both adiabatic and non-adiabatic cases, horizontal extension of
ion conics due to E×B drift, and evolution to elevated conics and
ion beams in the model. In the adiabatic case, the conic angle decreases with
increasing altitude much faster than was observed. The occurrence frequency of
small-angle conics is much larger than the observed value without E×B
drift and evolution to the other UFIs. An agreement is obtained by assuming
non-adiabatic variation of conic angles with altitude and an ion E×B
drift to gyro velocity ratio of 0.08 to 0.6, depending on geomagnetic
activities.
Key words. Ionosphere (particle acceleration) ·
Magnetospheric physics (auroral phenomena; magnetopause, cusp, and boundary
layers). |
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