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| Titel |
Response of ionospheric electric fields to variations in the interplanetary magnetic field |
| VerfasserIn |
S. P. Mishra, E. Nielsen |
| 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 ; 14, no. 8 ; Nr. 14, no. 8, S.794-802 |
| Datensatznummer |
250012382
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| Publikation (Nr.) |
 copernicus.org/angeo-14-794-1996.pdf |
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| Zusammenfassung |
| The STARE system (Scandinavian Twin Auroral
Radar Experiment) provides estimates of electron drift velocities, and hence
also of the electric field in the high-latitude E-region ionosphere between 65
and 70 degrees latitude. The occurrence of drift velocities larger than about
400 m/s (equivalent to an electric field of 20 mV/m) have been correlated with
the magnitude of the Interplanetary Magnetic Field (IMF) components Bz
and By at all local times. Observation days have been
considered during which both southward (Bz<0) and northward
(Bz>0) IMF occurred. The occurrence of electric fields
larger than 20 mV/m increases with increases in Bz magnitudes
when Bz<0. It is found that the effects of southward IMF
continue for some time following the northward turnings of the IMF. In order to
eliminate such residual effects for Bz<0, we have, in the
second part of the study, considered those days which were characterized by a
pure northward IMF. The occurrence is considerably lower during times when Bz>0,
than during those when Bz is negative. These results are
related to the expansion and contraction of the auroral oval. The different
percentage occurrences of large electric field for By>0 and
By<0 components of the IMF during times when Bz>0,
clearly display a dawn-dusk asymmetry of plasma flow in the ionosphere. The
effects of the time-varying solar-wind speed, density, IMF fluctuations, and
magnetospheric substorms on the occurrence of auroral-backscatter observations
are also discussed. |
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