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| Titel |
A study of quasi-periodic ELF-VLF emissions at three Antarctic stations: evidence for off-equatorial generation? |
| VerfasserIn |
K. Morrison, M. J. Engebretson, J. R. Beck, J. E. Johnson, R. L. Arnoldy, L. J. Cahill, D. L. Carpenter, M. Gallani |
| 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 ; 12, no. 2/3 ; Nr. 12, no. 2/3, S.139-146 |
| Datensatznummer |
250010315
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| Publikation (Nr.) |
 copernicus.org/angeo-12-139-1994.pdf |
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| Zusammenfassung |
| The spatial extent and temporal behaviour of
quasi-periodic (QP) intensity modulations of 0.5-2 kHz ELF-VLF signals were
investigated in a comparative study of data collected at the Antarctic stations
of South Pole (L=14), Halley (L=4), and Siple (L=4).
Frequently, the waveforms of ELF-VLF signals simultaneously received at each
site were identical. Although of similar frequency structure, the waveforms of
the accompanying Pc3 magnetic pulsations did not show a one-to-one association.
Whereas both are dayside phenomena, QP emissions occur over a smaller range of
local times, and have a maximum of occurrence later in the day closer to local
noon. QP emissions are identified with the periodic modulation of the electron
pitch-angle distribution by the propagation of ULF compressional fast-mode waves
through a region. However, contrary to previous ideas, rising-tone emissions do
not represent the frequency-time signatures of such waves. In addition to
generation close to the equatorial plane, we propose an additional high-latitude
source of QP emissions. These emissions are associated with regions of minimum B
produced by the dayside compression of the magnetosphere close to the
magnetopause. Model magnetic field calculations of these minimum-B
regions as a function of magnetic local time and invariant latitude are
presented. |
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