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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, 271–282, 2007
https://doi.org/10.5194/angeo-25-271-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 25, 271–282, 2007
https://doi.org/10.5194/angeo-25-271-2007
© Author(s) 2007. This work is distributed under
the Creative Commons Attribution 3.0 License.

  01 Feb 2007

01 Feb 2007

Diffusion at the Earth magnetopause: enhancement by Kelvin-Helmholtz instability

R. Smets1, G. Belmont1, D. Delcourt2, and L. Rezeau1 R. Smets et al.
  • 1CETP/CNRS/UVSQ/UPMC/IPSL, 10–12 Avenue de l'Europe, 78140 Vélizy, France
  • 2CETP/CNRS/UVSQ/UPMC/IPSL, 4 Avenue de Neptune, 94107 Saint Maur des Fossés, France

Abstract. Using hybrid simulations, we examine how particles can diffuse across the Earth's magnetopause because of finite Larmor radius effects. We focus on tangential discontinuities and consider a reversal of the magnetic field that closely models the magnetopause under southward interplanetary magnetic field. When the Larmor radius is on the order of the field reversal thickness, we show that particles can cross the discontinuity. We also show that with a realistic initial shear flow, a Kelvin-Helmholtz instability develops that increases the efficiency of the crossing process. We investigate the distribution functions of the transmitted ions and demonstrate that they are structured according to a D-shape. It accordingly appears that magnetic reconnection at the magnetopause is not the only process that leads to such specific distribution functions. A simple analytical model that describes the built-up of these functions is proposed.

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