Journal cover Journal topic
Annales Geophysicae An open-access journal of the European Geosciences Union
Ann. Geophys., 26, 929-940, 2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.
13 May 2008
Cluster observations on the thin current sheet in the magnetotail
C. L. Cai1,2, I. Dandouras1, H. Rème1, J. B. Cao2, G. C. Zhou2, and G. K. Parks3 1Centre d'Etude Spatiale des Rayonnements, Centre National de la Recherche Scientifique/Université Paul Sabatier, Toulouse 31028, France
2State Key Laboratory of Space Weather, Center for Space Science and Applied Research, Beijing 100080, China
3Space Sciences Laboratory, University of California, Berkeley, CA, 94720, USA
Abstract. A magnetotail event on 15 September 2001 is analyzed, during which the Cluster spacecraft observed both embedding and bifurcation of the Thin Current Sheet (TCS). It is indicated that the ion anisotropy and nongyrotropy are responsible for those new equilibrium features that represent deviations from the conventional Harris model. Measurements show that an embedded proton TCS manifests a pressure anisotropy with p||>p, simultaneously associated with a density embedding; while a bifurcated oxygen ion TCS exhibits a pressure anisotropy mainly with p||<p and nongrotropy, except at the edges where p||>p is the necessary marginal firehose stability condition. The local flapping motion of the TCS was observed, and some particular features such as the solitary wave-like behavior and the kink motion in the plane perpendicular to the Sun-Earth direction were revealed. The present investigation intimates the complexity of equilibria of the magnetotail current sheet and declares the crucial role played by the ion kinetics in the dynamics of TCSs.

Citation: Cai, C. L., Dandouras, I., Rème, H., Cao, J. B., Zhou, G. C., and Parks, G. K.: Cluster observations on the thin current sheet in the magnetotail, Ann. Geophys., 26, 929-940,, 2008.
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