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| Titel |
IMF effect on the polar cap contraction and expansion during a period of substorms |
| VerfasserIn |
A. T. Aikio, T. Pitkänen, I. Honkonen, M. Palmroth, O. Amm |
| 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 ; 31, no. 6 ; Nr. 31, no. 6 (2013-06-12), S.1021-1034 |
| Datensatznummer |
250019049
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| Publikation (Nr.) |
 copernicus.org/angeo-31-1021-2013.pdf |
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| Zusammenfassung |
The polar cap boundary (PCB) location and motion in the nightside ionosphere
has been studied by using measurements from the EISCAT radars and the MIRACLE
magnetometers during a period of four substorms on 18 February 2004. The OMNI
database has been used for observations of the solar wind and the Geotail
satellite for magnetospheric measurements. In addition, the event was
modelled by the GUMICS-4 MHD simulation. The simulation of the PCB location
was in a rather good agreement with the experimental estimates at the EISCAT
longitude. During the first three substorm expansion phases, neither the
local observations nor the global simulation showed any poleward motions of
the PCB, even though the electrojets intensified. Rapid poleward motions of
the PCB took place only in the early recovery phases of the substorms. Hence,
in these cases the nightside reconnection rate was locally higher in the
recovery phase than in the expansion phase.
In addition, we suggest that the IMF Bz component correlated with the
nightside tail inclination angle and the PCB location with about a 17-min
delay from the bow shock. By taking the delay into account, the IMF northward
turnings were associated with dipolarizations of the magnetotail and poleward
motions of the PCB in the recovery phase. The mechanism behind this effect
should be studied further. |
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