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Ann. Geophys., 25, 1471-1476, 2007
www.ann-geophys.net/25/1471/2007/
© European Geosciences Union 2007
The magnetic structure of an earthward-moving flux rope observed by Cluster in the near-tail
Y. C. Zhang1,2, Z. X. Liu1, C. Shen1, A. Fazakerley3, M. Dunlop4, H. Réme5, E. Lucek6, A. P. Walsh3, and L. Yao1,2
1State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Chinese Academy of Sciences, Beijing 100080, China
2Graduate School of the Chinese Academy of Sciences, Beijing 100080, China
3Mullard Space Science Laboratory, Univ. College London, London, UK
4Rutherford Appleton Laboratory, Chilton, DIDCOT, Oxfordshire OX11 0QX, UK
5Centre d'Etudes Spatiale des Rayonnements, BP 4346, 31028 Toulouse Cedex 4, France
6SAPG, Imperial College London SW7 2BZ, UK
Abstract. We investigate the magnetic structure of a small
earthward-moving flux rope observed by Cluster in the near-Earth plasma
sheet through application of the Grad-Shafranov (GS) technique to
reconstruct the transverse magnetic field distribution perpendicular to the
flux rope axis at X=−14.75 RE. We find that the principal axis of the flux
rope lies approximately along the dawn-dusk direction and that the diameter
of the flux rope is about 1.5 RE. There is a strong duskward core magnetic
field in the center of the flux rope. According to the AE index, there is no
obvious substorm associated with the magnetic flux rope. Recent studies
indicate that the formation of the flux rope in the plasma sheet can be
understood in terms of simultaneous reconnection at multiple X-line points
in the near-tail. The distribution of the transverse magnetic field on the
cross section is the asymmetric circles, which requires that the
reconnections at multiple X-line points occur. So our results also provide
additional evidence for the occurrence of multiple-X line reconnection in
the magnetotail.
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