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| Titel |
The statistical dependence of auroral absorption on geomagnetic and solar wind parameters |
| VerfasserIn |
A. J. Kavanagh, M. J. Kosch, F. Honary, A. Senior, S. R. Marple, E. E. Woodfield, I. W. McCrea |
| 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 ; 22, no. 3 ; Nr. 22, no. 3 (2004-03-19), S.877-887 |
| Datensatznummer |
250014808
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| Publikation (Nr.) |
 copernicus.org/angeo-22-877-2004.pdf |
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| Zusammenfassung |
Data from the Imaging Riometer for Ionospheric Studies (IRIS) at Kilpisjärvi,
Finland, have been compiled to form statistics of auroral absorption based on seven
years of observations. In a previous study a linear relationship between the logarithm
of the absorption and the Kp index provided a link between the observations of
precipitation with the level of geomagnetic activity. A better fit to the absorption data
is found in the form of a quadratic in Kp for eight magnetic local time sectors. Past
statistical investigations of absorption have hinted at the possibility of using the solar
wind velocity as a proxy for the auroral absorption, although the lack of available
satellite data made such an investigation difficult. Here we employ data from the solar
wind monitors, WIND and ACE, and derive a linear relationship between the solar
wind velocity and the cosmic noise absorption at IRIS for the same eight magnetic
local time sectors. As far as the authors are aware this is the first time that in situ
measurements of the solar wind velocity have been used to create a direct link with
absorption on a statistical basis. The results are promising although, it is clear that
some other factor is necessary in providing reliable absorption predictions. Due to the
substorm related nature of auroral absorption, this is likely formed by the recent time
history of the geomagnetic activity, or by some other indicator of the energy stored
within the magnetotail. For example, a dependence on the southward IMF
(interplanetary magnetic field) is demonstrated with absorption increasing with
successive decreases in Bz; a northward IMF appears to have little effect and neither
does the eastward component, By.
Key words. Magnetospheric physics (energetic particles,
precipitating; solar wind-magnetosphere interactions) –
Ionosphere (modeling and forecasting) |
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