Inner plasma structure of the low-latitude reconnection layer

Zhang, Q. -H. and Dunlop, M. W. and Lockwood, M. and Lavraud, B. and Bogdanova, Y. V. and Hasegawa, H. and Yang, H-G. and Liu, R. -Y. and Hu, H. -Q. and Zhang, B. -C. and Pu, Z. -Y. and Yang, Z. -W. and Wang, J. and Taylor, M. G. G. T. and Berchem, J. and Constantinescu, D. and Volwerk, M. and Frey, H. and Fazakerley, A. N. and Shen, C. and Shi, J. -K. and Sibeck, D. and Escoubet, P. and Wild, J. A. (2012) Inner plasma structure of the low-latitude reconnection layer. Journal of Geophysical Research - Space Physics, 117. -. ISSN 0148-0227

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Abstract

We report a clear transition through a reconnection layer at the low-latitude magnetopause which shows a complete traversal across all reconnected field lines during northwestward interplanetary magnetic field (IMF) conditions. The associated plasma populations confirm details of the electron and ion mixing and the time history and acceleration through the current layer. This case has low magnetic shear with a strong guide field and the reconnection layer contains a single density depletion layer on the magnetosheath side which we suggest results from nearly field-aligned magnetosheath flows. Within the reconnection boundary layer, there are two plasma boundaries, close to the inferred separatrices on the magnetosphere and magnetosheath sides (S-sp and S-sh) and two boundaries associated with the Alfven waves (or Rotational Discontinuities, RDsp and RDsh). The data are consistent with these being launched from the reconnection site and the plasma distributions are well ordered and suggestive of the time elapsed since reconnection of the field lines observed. In each sub-layer between the boundaries the plasma distribution is different and is centered around the current sheet, responsible for magnetosheath acceleration. We show evidence for a velocity dispersion effect in the electron anisotropy that is consistent with the time elapsed since reconnection. In addition, new evidence is presented for the occurrence of partial reflection of magnetosheath electrons at the magnetopause current layer.

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