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| Titel |
Reconfiguration and closure of lobe flux by reconnection during northward IMF: possible evidence for signatures in cusp/cleft auroral emissions |
| VerfasserIn |
M. Lockwood, J. Moen |
| 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 ; 17, no. 8 ; Nr. 17, no. 8, S.996-1011 |
| Datensatznummer |
250013795
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| Publikation (Nr.) |
 copernicus.org/angeo-17-996-1999.pdf |
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| Zusammenfassung |
Observations are presented of the response of
the dayside cusp/cleft aurora to changes in both the clock and elevation angles
of the interplanetary magnetic field (IMF) vector, as monitored by the WIND
spacecraft. The auroral observations are made in 630 nm light at the winter
solstice near magnetic noon, using an all-sky camera and a meridian-scanning
photometer on the island of Spitsbergen. The dominant change was the response to
a northward turning of the IMF which caused a poleward retreat of the dayside
aurora. A second, higher-latitude band of aurora was seen to form following the
northward turning, which is interpreted as the effect of lobe reconnection which
reconfigures open flux. We suggest that this was made possible in the winter
hemisphere, despite the effect of the Earth's dipole tilt, by a relatively large
negative X component of the IMF. A series of five events then formed in the
poleward band and these propagated in a southwestward direction and faded at the
equatorward edge of the lower-latitude band as it migrated poleward. It is shown
that the auroral observations are consistent with overdraped lobe flux being
generated by lobe reconnection in the winter hemisphere and subsequently being
re-closed by lobe reconnection in the summer hemisphere. We propose that the
balance between the reconnection rates at these two sites is modulated by the
IMF elevation angle, such that when the IMF points more directly northward, the
summer lobe reconnection site dominates, re-closing all overdraped lobe flux and
eventually becoming disconnected from the Northern Hemisphere.
Key words. Magnetospheric physics (magnetopause · cusp
and boundary layers; solar-wind-magnetosphere interactions) · Space plasma
physics (magnetic reconnection) |
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