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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 22, issue 3
Ann. Geophys., 22, 971–983, 2004
https://doi.org/10.5194/angeo-22-971-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 22, 971–983, 2004
https://doi.org/10.5194/angeo-22-971-2004
© Author(s) 2004. This work is distributed under
the Creative Commons Attribution 3.0 License.

  19 Mar 2004

19 Mar 2004

Cluster observations of surface waves on the dawn flank magnetopause

C. J. Owen1, M. G. G. T. Taylor4,1, I. C. Krauklis1, A. N. Fazakerley1, M. W. Dunlop2,5, and J. M. Bosqued3 C. J. Owen et al.
  • 1Mullard Space Science Laboratory, Department of Space and Climate Physics, University College London, Holmbury St. Mary, Dorking, Surrey, RH5 6NT, UK
  • 2Blackett Laboratory, Imperial College of Science Technology and Medicine, Prince Consort Road, London, SW7 2BZ, UK
  • 3CESR/CNRS, BP 4346 9, Avenue Colonel Roche, 31028 Toulouse Cedex, France
  • 4Now at Los Alamos National Laboratory, Los Alamos, NM, USA
  • 5Now at Rutherford Appleton Laboratory, Didcot, Oxon, UK

Abstract. On 14 June 2001 the four Cluster spacecraft recorded multiple encounters of the dawn-side flank magnetopause. The characteristics of the observed electron populations varied between a cold, dense magnetosheath population and warmer, more rarified boundary layer population on a quasi-periodic basis. The demarcation between these two populations can be readily identified by gradients in the scalar temperature of the electrons. An analysis of the differences in the observed timings of the boundary at each spacecraft indicates that these magnetopause crossings are consistent with a surface wave moving across the flank magnetopause. When compared to the orientation of the magnetopause expected from models, we find that the leading edges of these waves are approximately 45° steeper than the trailing edges, consistent with the Kelvin-Helmholtz (KH) driving mechanism. A stability analysis of this interval suggests that the magnetopause is marginally stable to this mechanism during this event. Periods in which the analysis predicts that the magnetopause is unstable correspond to observations of greater wave steepening. Analysis of the pulses suggests that the waves have an average wavelength of approximately 3.4 RE and move at an average speed of ~65km s-1 in an anti-sunward and northward direction, despite the spacecraft location somewhat south of the GSE Z=0 plane. This wave propagation direction lies close to perpendicular to the average magnetic field direction in the external magnetosheath, suggesting that these waves may preferentially propagate in the direction that requires no bending of these external field lines

Key words. Magnetospheric physics (magnetospheric configuration and dynamics; MHD waves and unstabilities; solar wind-magnetosphere interactions)

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