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Annales Geophysicae An interactive open-access journal of the European Geosciences Union
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Volume 23, issue 10
Ann. Geophys., 23, 3389–3398, 2005
https://doi.org/10.5194/angeo-23-3389-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.
Ann. Geophys., 23, 3389–3398, 2005
https://doi.org/10.5194/angeo-23-3389-2005
© Author(s) 2005. This work is distributed under
the Creative Commons Attribution 3.0 License.

  30 Nov 2005

30 Nov 2005

Electron dynamics during substorm dipolarization in Mercury's magnetosphere

D. C. Delcourt1, K. Seki2, N. Terada2,*, and Y. Miyoshi2 D. C. Delcourt et al.
  • 1CETP-CNRS-IPSL, Saint-Maur des Fossés, France
  • 2STEL, Nagoya University, Toyokawa, Japan
  • *now at: NIICT, Tokyo and CREST-JSTA, Saitama, Japan

Abstract. We examine the nonlinear dynamics of electrons during the expansion phase of substorms at Mercury using test particle simulations. A simple model of magnetic field line dipolarization is designed by rescaling a magnetic field model of the Earth's magnetosphere. The results of the simulations demonstrate that electrons may be subjected to significant energization on the time scale (several seconds) of the magnetic field reconfiguration. In a similar manner to ions in the near-Earth's magnetosphere, it is shown that low-energy (up to several tens of eV) electrons may not conserve the second adiabatic invariant during dipolarization, which leads to clusters of bouncing particles in the innermost magnetotail. On the other hand, it is found that, because of the stretching of the magnetic field lines, high-energy electrons (several keVs and above) do not behave adiabatically and possibly experience meandering (Speiser-type) motion around the midplane. We show that dipolarization of the magnetic field lines may be responsible for significant, though transient, (a few seconds) precipitation of energetic (several keVs) electrons onto the planet's surface. Prominent injections of energetic trapped electrons toward the planet are also obtained as a result of dipolarization. These injections, however, do not exhibit short-lived temporal modulations, as observed by Mariner-10, which thus appear to follow from a different mechanism than a simple convection surge.

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