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| Titel |
Pulsed flows observed during an interval of prolonged northward IMF |
| VerfasserIn |
G. Provan, Mark Lester, A. Grocott, S. W. H. Cowley |
| 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 ; 23, no. 4 ; Nr. 23, no. 4 (2005-06-03), S.1207-1225 |
| Datensatznummer |
250015217
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| Publikation (Nr.) |
 copernicus.org/angeo-23-1207-2005.pdf |
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| Zusammenfassung |
| On the 22 December 2002 the interplanetary magnetic field (IMF) was directed
northwards for more than 12h. The Northern and Southern Hemisphere
SuperDARN radars were used to study global high-latitude convection during
this interval, complemented by data from the ACE and DMSP F13 spacecraft.
The relative magnitudes of the IMF By and Bz components varied
during this period. When the magnitude of the By component was
comparable with or dominated the Bz component, signatures of
simultaneous low-latitude and lobe reconnection were observed. Specifically
two "standard" merging cells were observed in both hemispheres. In the
Northern Hemisphere a high-latitude lobe cell was observed within the dusk
merging cell, and there was also evidence of a narrow viscous cell located
equatorward of this lobe cell. We observed the ionospheric signatures of
flux transfer events (FTEs) in both the Northern and Southern Hemispheres,
occurring with a periodicity of ~15min. In the Northern Hemisphere
the FTEs were associated with a stepwise equatorward progression of the
equatorward boundary of radar backscatter on the dayside. When the IMF
Bz component was predominantly greater than the IMF By component,
we observed a four-cell convection pattern in the Northern Hemisphere, with
pulses of reverse reconnection and an associated stepwise poleward
retraction of the equatorward boundary of radar backscatter occurring every
~25min. These observations are consistent with pulsed lobe
reconnection occurring in both hemispheres, closing open flux and adding
closed flux to the dayside magnetopause. So, during this northward IMF
interval the location of the sites of reconnection between the IMF and the
Earth's magnetosphere, and thus the form of reconnection process, varied
with changing IMF conditions. However, the reconnection remained pulsed,
with lobe-only reconnection having a significantly longer periodicity
compared with simultaneous lobe and low-latitude reconnection. |
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