Journal cover Journal topic
Annales Geophysicae An interactive open-access journal of the European Geosciences Union
Journal topic

Journal metrics

Journal metrics

  • IF value: 1.490 IF 1.490
  • IF 5-year value: 1.445 IF 5-year
    1.445
  • CiteScore value: 2.9 CiteScore
    2.9
  • SNIP value: 0.789 SNIP 0.789
  • IPP value: 1.48 IPP 1.48
  • SJR value: 0.74 SJR 0.74
  • Scimago H <br class='hide-on-tablet hide-on-mobile'>index value: 88 Scimago H
    index 88
  • h5-index value: 21 h5-index 21
Volume 26, issue 8
Ann. Geophys., 26, 2471–2483, 2008
https://doi.org/10.5194/angeo-26-2471-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 26, 2471–2483, 2008
https://doi.org/10.5194/angeo-26-2471-2008
© Author(s) 2008. This work is distributed under
the Creative Commons Attribution 3.0 License.

  15 Aug 2008

15 Aug 2008

Effects on magnetic reconnection of a density asymmetry across the current sheet

K. G. Tanaka1, A. Retinò2,3, Y. Asano4, M. Fujimoto1, I. Shinohara1, A. Vaivads3, Y. Khotyaintsev3, M. André3, M. B. Bavassano-Cattaneo5, S. C. Buchert3, and C. J. Owen6 K. G. Tanaka et al.
  • 1Japan Aeronautical Exploration Agency, Kanagawa, Japan
  • 2Space Research Institute, Austrian Academy of Sciences, Graz, Austria
  • 3IRFU, Uppsala, Sweden
  • 4Tokyo Institute of Technology, Japan
  • 5IFSI-INAF, Roma, Italy
  • 6MSSL, London, UK

Abstract. The magnetopause (MP) reconnection is characterized by a density asymmetry across the current sheet. The asymmetry is expected to produce characteristic features in the reconnection layer. Here we present a comparison between the Cluster MP crossing reported by Retinò et al. (2006) and virtual observations in two-dimensional particle-in-cell simulation results. The simulation, which includes the density asymmetry but has zero guide field in the initial condition, has reproduced well the observed features as follows: (1) The prominent density dip region is detected at the separatrix region (SR) on the magnetospheric (MSP) side of the MP. (2) The intense electric field normal to the MP is pointing to the center of the MP at the location where the density dip is detected. (3) The ion bulk outflow due to the magnetic reconnection is seen to be biased towards the MSP side. (4) The out-of-plane magnetic field (the Hall magnetic field) has bipolar rather than quadrupolar structure, the latter of which is seen for a density symmetric case. The simulation also showed rich electron dynamics (formation of field-aligned beams) in the proximity of the separatrices, which was not fully resolved in the observations. Stepping beyond the simulation-observation comparison, we have also analyzed the electron acceleration and the field line structure in the simulation results. It is found that the bipolar Hall magnetic field structure is produced by the substantial drift of the reconnected field lines at the MSP SR due to the enhanced normal electric field. The field-aligned electrons at the same MSP SR are identified as the gun smokes of the electron acceleration in the close proximity of the X-line. We have also analyzed the X-line structure obtained in the simulation to find that the density asymmetry leads to a steep density gradient in the in-flow region, which may lead to a non-stationary behavior of the X-line when three-dimensional freedom is taken into account.

Publications Copernicus
Download
Citation