Particle acceleration in time‐developing magnetic reconnection process

Authors:
  • TSTetsuya Sato
    Tetsuya Sato
  • HMHiroshi Matsumoto
    Hiroshi Matsumoto
  • KNKeisuke Nagai
    Keisuke Nagai
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Abstract
Particle trajectories are numerically followed in the presence of space‐ and time‐varying electric and magnetic fields that are obtained by the previous two‐dimensional magnetohydrodynamic (MHD) simulation of X type magnetic reconnection process (Hayashi and Sato, 1978). Two conclusions are notable. First, those particles that encounter a slow shock layer associated with the reconnection process suffer an abrupt and large orbit modification whereby they gain an energy roughly by one order larger than that corresponding to the Alfven speed, i.e., several electron volts for electrons and 10 keV for protons. Second, particles that are driven toward the neutral sheet by the E × B drift are accelerated almost instantaneously up to an energy range of auroral particles (1–10 keV for electrons and 10–100 keV for protons) when they reach near the X type neutral line, some leaving the neutral sheet immediately and others executing meandering motions for some time before leave. An important finding is that a meandering particle can leave the neutral sheet along a reconnected field line because reconnection proceeds and fields change in time. However, their pitch angles are usually larger than the loss cone angle so that they would not be able to be auroral particles in a direct way.

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