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Ann. Geophys., 25, 1669-1690, 2007
www.ann-geophys.net/25/1669/2007/
© European Geosciences Union 2007
Motion of flux transfer events: a test of the Cooling model
R. C. Fear1, S. E. Milan1, A. N. Fazakerley2, C. J. Owen2, T. Asikainen3, M. G. G. T. Taylor4, E. A. Lucek5, H. Rème6, I. Dandouras6, and P. W. Daly7
1Department of Physics and Astronomy, University of Leicester, Leicester, LE1 7RH, UK
2Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
3Department of Physical Sciences, University of Oulu, P.O. Box 3000, 90014, Finland
4Research and Scientific Support Department, European Space Agency, 2201AZ Noordwijk, The Netherlands
5Blackett Laboratory, Imperial College, Prince Consort Road, London, SW7 2BZ, UK
6CESR/CNRS, 9 Avenue du Colonel Roche, B.P. 4346, 31028 Toulouse Cedex 4, France
7Max-Planck-Institut für Sonnensystemforschung, Max-Planck-Str. 2, 37191 Katlenburg-Lindau, Germany
Abstract. The simple model of reconnected field line motion developed by
Cooling
et al. (2001) has been used in several recent case studies to
explain the motion of flux transfer events across the magnetopause. We
examine 213 FTEs observed by all four Cluster spacecraft under a variety of
IMF conditions between November 2002 and June 2003, when the spacecraft
tetrahedron separation was ~5000 km. Observed velocities were
calculated from multi-spacecraft timing analysis, and compared with the
velocities predicted by the Cooling model in order to check the validity of
the model. After excluding three categories of FTEs (events with poorly
defined velocities, a significant velocity component out of the magnetopause
surface, or a scale size of less than 5000 km), we were left with a
sample of 118 events. 78% of these events were consistent in both direction
of motion and speed with one of the two model de Hoffmann-Teller (dHT)
velocities calculated from the Cooling model (to within 30° and a
factor of two in the speed). We also examined the plasma signatures of
several magnetosheath FTEs; the electron signatures confirm the hemisphere of
connection indicated by the model in most cases. This indicates that although
the model is a simple one, it is a useful tool for identifying the source
regions of FTEs.
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