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Ann. Geophys., 23, 461-473, 2005
www.ann-geophys.net/23/461/2005/
© European Geosciences Union 2005
Cluster multispacecraft observations at the high-latitude duskside magnetopause: implications for continuous and component magnetic reconnection
A. Retinò1, M. B. Bavassano Cattaneo2, M. F. Marcucci2, A. Vaivads1, M. André1, Y. Khotyaintsev1, T. Phan3, G. Pallocchia2, H. Rème4, E. Möbius5, B. Klecker6, C. W. Carlson3, M. McCarthy7, A. Korth8, R. Lundin9, and A. Balogh10
1Swedish Institute of Space Physics, Uppsala, Sweden
2IFSI-CNR, Roma, Italy
3University of California, Berkeley, USA
4CESR, Toulouse, France
5University of New Hampshire, Durham, USA
6MPE, Garching, Germany
7University of Washington, Seattle, USA
8MPS, Lindau, Germany
9Swedish Institute of Space Physics, Kiruna, Sweden
10Imperial College, London, UK
Abstract. We report multispacecraft Cluster observations of magnetic
reconnection at the high-latitude magnetopause/magnetospheric
boundary layer (MP/BL) under mainly northward interplanetary
magnetic field (IMF) conditions. The event we study is on 3 December
2001 when the Cluster spacecraft were skimming the high-latitude
duskside MP/BL during a period of about four hours. The orbit and
configuration of the spacecraft were such that at least one
satellite was present in the MP/BL during most of that period. We
present the evidence of reconnection in the form of tangential stress
balance between the magnetosheath and the MP/BL (Walén test) and
in several cases in the form of transmitted magnetosheath ions in
the MP/BL and incident/reflected magnetosheath ions in the
magnetosheath boundary layer (MSBL) . The observations are
consistent with magnetic reconnection occurring tailward of the cusp
and going on continuously for a period of about four hours. The
observed directions of the reconnection flows are consistent with
the IMF orientation, thus indicating that reconnection is globally
controlled by the IMF. Observations of a few flow reversals suggest
passages of the spacecraft close to the X-line. The observation of
low magnetic shear across the magnetopause during a flow reversal is
consistent with component merging at least in one case. The
observation of reconnection flows on the duskside magnetopause
irrespective of the change in the sign of the IMF BY also
suggests a better agreement with the component merging model, though
antiparallel merging cannot be excluded because the distance from
the X-line is not known.
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