Suprathermal electron acceleration in magnetic reconnection

The suprathermal electrons of ≥20 keV that extend from the hot thermal electron with 2–3 keV temperature are sometimes observed in Earth's magnetosphere in association with reconnection. We study the origin of the hot and suprathermal electrons in terms of the kinetic magnetic reconnection process by using the two-dimensional particle-in-cell simulation. We find that the hot and suprathermal electrons can be formed in the nonlinear evolution of a large-scale magnetic reconnection. The electrons are, at the first stage, accelerated in the elongated, thin, X-type current sheet. Next the preheated/accelerated electrons are transported to the stronger magnetic field region produced by piling up of magnetic field lines due to colliding of the fast reconnection outflow with the preexisting plasma. In this region they are further accelerated owing to the ∇B drift and the curvature drift. The mirror force of the reconnecting magnetic fields, the effective pitch angle scattering that occurs when the Larmor radius is comparable to the magnetic field line curvature radius, and the broadband waves excited by the Hall electric current are the other important agents to control the particle acceleration.

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