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| Titel |
An unusual strolling motion of polar cap patches: an implication of the influence of tail reconnection on the nightside polar cap convection |
| VerfasserIn |
K. Hosokawa, J. I. Moen, P. T. Jayachandran, K. Shiokawa, Y. Otsuka |
| 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 |
250060588
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| Zusammenfassung |
| On January 12, 2005, a successive appearance of polar cap patches on the nightside
was observed in the image captured by an all-sky imager (ASI) at Resolute Bay,
Canada (74.73°N, 265.07°E). During the interval, the patches showed an unusual
strolling motion in which their moving direction was very drastically changed twice
(antisunward-dawnward-duskward). One may suspect that such changes in motion were
caused by the reconfiguration of the polar cap convection due to a change in the IMF By.
However, there were no remarkable variations in the sign of the IMF By in the solar wind
data, which indicates that the unusual behavior of the patches was independent
of the IMF-driven polar cap convection changes. Before the first change in the
motion occurred, a transient bright aurora appeared in the equatorward part of the
field-of-view in the dawn side. Immediately after the appearance of the transient auroral
feature, the direction of the motion of the patches changed from anti-sunward to
dawnward as if the patches were drawn into the aurora. After the disappearance of
the aurora, the patches once almost stagnated but subsequently started to move
duskward and anti-sunward. We interpret the bright auroral feature as a signature of the
poleward boundary intensification (PBI), which is an ionospheric manifestation of an
enhanced reconnection in the magnetotail. Accordingly, we speculate that an excited
flow across the open-closed field line boundary redirected the anti-sunward polar
cap convection towards the PBI and then allowed the patches to be drawn into the
aurora near the polar cap boundary. This study indicates the importance of the tail
reconnection as a driver of the nightside polar cap convection, resulting in the dynamical
characteristics of polar cap patches; this relation may enable us to monitor the activity
of the tail reconnection by using the motion of polar cap patches as an indicator. |
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