Evidence for newly closed magnetosheath field lines at the dayside magnetopause under northward IMF

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Read Full Article (file size: 1316059 bytes) Cited by JOURNAL OF GEOPHYSICAL RESEARCH, VOL. 111, A05211, doi:10.1029/2005JA011266, 2006 Evidence for newly closed magnetosheath field lines at the dayside magnetopause under northward IMF B. Lavraud Space Science and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico, USA M. F. Thomsen Space Science and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico, USA B. Lefebvre Blackett Laboratory, Imperial College, London, UK S. J. Schwartz Blackett Laboratory, Imperial College, London, UK K. Seki Solar-Terrestrial Environment Laboratory, University of Nagoya, Aichi, Japan T. D. Phan Space Sciences Laboratory, University of California, Berkeley, Berkeley, California, USA Y. L. Wang Space Science and Applications, Los Alamos National Laboratory, Los Alamos, New Mexico, USA A. Fazakerley Mullard Space Science Laboratory, Surrey, UK H. Rème Centre d'Etude Spatiale des Rayonnements, Toulouse, France A. Balogh Blackett Laboratory, Imperial College, London, UK Abstract We analyze the structure of the high-latitude magnetopause under steady interplanetary magnetic field (IMF). We use 56 magnetopause encounters of Cluster spacecraft from 2001 to 2003 to explore the statistical properties of the magnetosheath electron boundary layer, observed outside the high-latitude dayside magnetopause. We focus on the occurrence of low absolute parallel heat flux in this layer and its dependence on the magnetic field clock angle simultaneously measured by Cluster. The low absolute parallel heat fluxes result from the presence of bidirectional heated electrons in the magnetosheath electron boundary layer and are primarily observed when the local magnetic field is northward. The bidirectional heated electrons are interpreted as the signature of newly closed magnetosheath field lines that have reconnected at the high-latitude magnetopause, tailward of the cusp, in both hemispheres. This study strongly suggests that double high-latitude reconnection is a tenable mechanism for the formation of the low-latitude boundary layer and potentially of the cold, dense plasma sheet under northward IMF. Although the efficiency (in terms of mass and energy transfer) of this mechanism is still to be investigated, it is an obvious way of capturing solar wind plasma under northward IMF. Received 13 June 2005; accepted 1 February 2006; published 26 May 2006. Keywords: boundary layer; magnetopause structure. Index Terms: 2724 Magnetospheric Physics: Magnetopause and boundary layers; 2723 Magnetospheric Physics: Magnetic reconnection (7526, 7835); 2706 Magnetospheric Physics: Cusp; 2784 Magnetospheric Physics: Solar wind/magnetosphere interactions. Read Full Article (file size: 1316059 bytes) Cited by Citation: Lavraud, B., M. F. Thomsen, B. Lefebvre, S. J. Schwartz, K. Seki, T. D. Phan, Y. L. Wang, A. Fazakerley, H. Rème, and A. Balogh (2006), Evidence for newly closed magnetosheath field lines at the dayside magnetopause under northward IMF, J. Geophys. Res., 111, A05211, doi:10.1029/2005JA011266. Copyright 2006 by the American Geophysical Union.

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