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| Titel |
Pc2-3 geomagnetic pulsations on the ground, in the ionosphere, and in the magnetosphere: MM100, CHAMP, and THEMIS observations |
| VerfasserIn |
N. Yagova, B. Heilig, E. Fedorov |
| 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 ; 33, no. 1 ; Nr. 33, no. 1 (2015-01-28), S.117-128 |
| Datensatznummer |
250121155
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| Publikation (Nr.) |
 copernicus.org/angeo-33-117-2015.pdf |
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| Zusammenfassung |
| We analyze Pc2-3 pulsations recorded by the CHAMP (CHAllenging Minisatellite
Payload) satellite in the F layer of the Earth's ionosphere, on the ground,
and in the magnetosphere during quiet geomagnetic conditions. The spectra of
Pc2-3 pulsations recorded in the F layer are enriched with frequencies above
50 mHz in comparison to the ground Pc2-3 spectra. These frequencies are
higher than the fundamental harmonics of the field line resonances in the
magnetosphere. High quality signals with dominant frequencies 70–200 mHz
are a regular phenomenon in the F layer and in the magnetosphere. The mean
latitude of the maximum Pc2-3 occurrence rate lies at L ≈ 3.5 in the
F layer, i.e., inside the plasmasphere. Day-to-day variations of the
L value of the CHAMP Pc2-3 occurrence rate maximum follow the plasmapause
day-to-day variations. Polarization and amplitude of Pc2-3s in the
magnetosphere, in the ionosphere, and on the ground allow us to suggest that
they are generated as fast magnetosonic (FMS) waves in the outer
magnetosphere and are partly converted into shear Alfven waves near the
plasmapause. The observed ground-to-ionosphere amplitude ratio during the
night is interpreted as a result of the Alfven wave transmission through the
ionosphere. The problem of wave transmission through the ionosphere is solved
theoretically by means of a numerical solution of the full-wave equation for
the Alfven wave reflection from and transmission through a horizontally
stratified ionosphere. The best agreement between the calculated and measured
values of the ground-to-ionosphere amplitude ratio is found for k = 5 ×
10−3 km−1, i.e., the observed ground-to-ionosphere amplitude ratio
corresponds to a wave spatial scale which could provide a Doppler shift
within a few percent of the apparent frequency of the Pc2-3 pulsations as
recorded by a low-orbiting spacecraft. |
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