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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 25, issue 1
Ann. Geophys., 25, 219-238, 2007
https://doi.org/10.5194/angeo-25-219-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 25, 219-238, 2007
https://doi.org/10.5194/angeo-25-219-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.

  01 Feb 2007

01 Feb 2007

On the location of dayside magnetic reconnection during an interval of duskward oriented IMF

J. A. Wild1, S. E. Milan2, J. A. Davies3, M. W. Dunlop3, D. M. Wright2, C. M. Carr4, A. Balogh4, H. Rème5, A. N. Fazakerley6, and A. Marchaudon6,* J. A. Wild et al.
  • 1Dept. of Communication Systems, Lancaster University, Lancaster, LA1 4WA, UK
  • 2Dept. of Physics & Astronomy, University of Leicester, Leicester, LE1 7RH, UK
  • 3Rutherford Appleton Laboratory, Didcot, Oxfordshire, OX11 0QX, UK
  • 4Blackett Laboratory, Imperial College, London SW7 2BZ, UK
  • 5CESR/CNRS, 9 Avenue du Colonel Roche BP 4346, 31028 Toulouse, Cedex 4, France
  • 6Mullard Space Science Laboratory, University College London, Holmbury St. Mary, Dorking, Surrey RH5 6NT, UK
  • *now at: LPCE/CNRS and Université d'Orléans, Orléans, France

Abstract. We present space- and ground-based observations of the signatures of magnetic reconnection during an interval of duskward-oriented interplanetary magnetic field on 25 March 2004. In situ field and plasma measurements are drawn from the Double Star and Cluster satellites during traversals of the pre-noon sector dayside magnetopause at low and high latitudes, respectively. These reveal the typical signatures of flux transfer events (FTEs), namely bipolar perturbations in the magnetic field component normal to the local magnetopause, enhancements in the local magnetic field strength and mixing of magnetospheric and magnetosheath plasmas. Further evidence of magnetic reconnection is inferred from the ground-based signatures of pulsed ionospheric flow observed over an extended interval. In order to ascertain the location of the reconnection site responsible for the FTEs, a simple model of open flux tube motion over the surface of the magnetopause is employed. A comparison of the modelled and observed motion of open flux tubes (i.e. FTEs) and plasma flow in the magnetopause boundary layer indicates that the FTEs observed at both low and high latitudes were consistence with the existence of a tilted X-line passing through the sub-solar region, as suggested by the component reconnection paradigm. While a high latitude X-line (as predicted by the anti-parallel description of reconnection) may have been present, we find it unlikely that it could have been responsible for the FTEs observed in the pre-noon sector under the observed IMF conditions. Finally, we note that throughout the interval, the magnetosphere was bathed in ULF oscillations within the solar wind electric field. While no one-to-one correspondence with the pulsed reconnection rate suggested by the ground-based observation of pulsed ionospheric flow has been demonstrated, we note that similar periodicity oscillations were observed throughout the solar wind-magnetosphere-ionosphere system. These findings are consistent with previously proposed mechanisms of solar wind modulation of the dayside reconnection rate.

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