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| Titel |
The variability of Joule heating, and its effects on the ionosphere and thermosphere |
| VerfasserIn |
A. S. Rodger, G. D. Wells, R. J. Moffett, G. J. Bailey |
| 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 ; 19, no. 7 ; Nr. 19, no. 7, S.773-781 |
| Datensatznummer |
250014288
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| Publikation (Nr.) |
 copernicus.org/angeo-19-773-2001.pdf |
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| Zusammenfassung |
A considerable fraction
of the solar wind energy that crosses the magnetopause ends up in the
high-latitude thermosphere-ionosphere system as a result of Joule heating, the
consequences of which are very significant and global in nature. Often Joule
heating calculations use hourly averages of the electric field, rather than the
time-varying electric field. This leads to an underestimation of the heating.
In this paper, we determine the magnitude of the underestimation of Joule
heating by analysing electric field data from the EISCAT Incoherent Scatter
Radar, situated at the 67° E magnetic latitude. We find that the
underestimation, using hourly-averaged electric field values, is normally ~20%,
with an upper value of about 65%. We find that these values are
insensitive to changes in solar flux, magnetic activity and magnetic local
time, implying that the electric field fluctuations are linear related to the
amplitude of the electric field. Assuming that these changes are representative
of the entire auroral oval, we then use a coupled ionosphere-thermosphere model
to calculate the local changes these underestimations in the heating rate cause
to the neutral temperature, mean molecular mass and meridional wind. The
changes in each parameter are of the order of a few percent but they result in
a reduction in the peak F-region concentration of ~20% in the summer
hemisphere at high latitudes, and about half of this level in the winter
hemisphere. We suggest that these calculations could be used to add corrections
to modelled values of Joule heating.
Key words. Ionosphere (eletric
fields and currents; ionospheric disturbances; polar ionosphere) |
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