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Titel |
Changes in the magnetotail configuration before near-Earth reconnection |
VerfasserIn |
K. Snekvik, E. Tanskanen, N. Østgaard, L. Juusola, K. Laundal, E. I. Gordeev, A. L. Borg |
Konferenz |
EGU General Assembly 2012
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Medientyp |
Artikel
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Sprache |
Englisch
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Digitales Dokument |
PDF |
Erschienen |
In: GRA - Volume 14 (2012) |
Datensatznummer |
250066166
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Zusammenfassung |
We have examined three typical substorm growth phase signatures in the magnetotail two
hours before near Earth reconnection; namely current sheet thinning, field line
stretching and increase in the lobe magnetic pressure. The reconnection events were
identified from in situ measurements in the plasma sheet by the Cluster spacecraft.
The events were signified by high speed plasma flows, often lasting more than one
hour. The list of events contains time intervals with high solar wind driving and
strong intensification in the auroral westward electrojet, and other intervals with
weak driving and no intensification in the electrojet. Irrespective of the amount of
driving, there was usually a significant thinning of the current sheet prior to the
reconnection onsets. Multi-spacecraft measurements of the magnetic field revealed that the
average thinning was from 24000 to 12000Â km, lasting about an hour. In those
events without thinning, the current sheet was thin for an extended period before
reconnection. Furthermore, the thinning happens even when there is no increase in the lobe
magnetic pressure in the same time interval. The magnetotail is often stretched for a
long time before reconnection onset, and reconnection seems to commence only
when the current sheet is thin enough. In those events with large increase in the
lobe magnetic pressure before onset, there is also significant field line stretching. |
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