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Ann. Geophys., 25, 1025-1035, 2007
www.ann-geophys.net/25/1025/2007/
© European Geosciences Union 2007
Global and local disturbances in the magnetotail during reconnection
T. V. Laitinen1, R. Nakamura2, A. Runov2, H. Rème3, and E. A. Lucek4
1Finnish Meteorological Institute, Space Research, PL 503, 00101 Helsinki, Finland
2Space Research Institute, Austrian Academy of Sciences, 8042 Graz, Austria
3Centre d'Etude Spatiale des Rayonnements, Toulouse, France
4The Blackett Laboratory, Imperial College, London, UK
Abstract. We examine Cluster observations of a reconnection event at
xGSM=−15.7 RE in the magnetotail on 11 October 2001,
when Cluster recorded the current sheet for an extended period
including the entire duration of the reconnection event. The onset
of reconnection is associated with a sudden orientation change of
the ambient magnetic field, which is also observed simultaneously by
Goes-8 at geostationary orbit. Current sheet oscillations are
observed both before reconnection and during it. The speed of the
flapping motions is found to increase when the current sheet
undergoes the transition from quiet to active state, as suggested by
an earlier statistical result and now confirmed within one single
event. Within the diffusion region both the tailward and earthward
parts of the quadrupolar magnetic Hall structure are recorded as an
x-line passes Cluster. We report the first observations of the Hall
structure conforming to the kinks in the current sheet. This results
in relatively strong fluctuations in Bz, which are shown to be
the Hall signature tilted in the yz plane with the current sheet.
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