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| Titel |
Evidence of more efficient whistler-mode transmission during periods of increased magnetic activity |
| VerfasserIn |
N. R. Thomson, M. A. Clilverd, A. J. Smith |
| 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 ; 15, no. 8 ; Nr. 15, no. 8, S.999-1004 |
| Datensatznummer |
250012907
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| Publikation (Nr.) |
 copernicus.org/angeo-15-999-1997.pdf |
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| Zusammenfassung |
| In a previous study it was reported that
whistler- mode signals received at Faraday, Antarctica (65°S,64°W)
and Dunedin, New Zealand (46°S,171°E)
with entry regions in Pacific longitudes (typically from the VLF transmitter NLK,
Seattle, USA) showed an increase in transmission of wave energy as magnetic
activity increased. However, signals with entry regions in Atlantic longitudes
(typically from the NSS transmitter, Annapolis, USA) did not appear to show such
a relationship. This paper reports the results of a study of the same two
longitude ranges but with the opposite transmitter providing additional
whistler-mode signal information, with L-values in the range 1.8–2.6.
Transmissions from NLK once again indicate a relationship between the
transmission of wave energy and magnetic activity even though the signals were
propagating in Atlantic longitudes, not Pacific. Any trend in NSS events
observed at Dunedin was obscured by a limited range of magnetic activity, and
duct exit regions so close to the receiver that small-scale excitation effects
appeared to be occurring. However, by combining data from both longitudes, i.e
Pacific and Atlantic, and using only ducts with exit regions that were >500km
from the receiver, NSS events were found to show the same trend as NLK events.
No significant longitude-dependent or transmitter-dependent variations in duct
efficiency could be detected. Duct efficiency increases by a factor of about 30
with Kp=2–8 and this result is discussed in terms of changes
in wave-particle interactions and duct size. |
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