Numerical Methods for Plasma Astrophysics:
From Particle Kinetics to MHD

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Magnetic Reconnection for Moderate Guide Fields: Kinetic Physics and Simulation Requirements

Dr. Michael Hesse

NASA

Abstract:   Collisionless magnetic reconnection is well-known to operate in systems with small to moderate guide magnetic field components. We refer to guide magnetic fields as "moderate" if their magnetude is of the same order as the reconnecting magnetic field components. Recent kinetic studies of such systems indicate that electron demagnetization should be based on the generation of gradient scale lengths, which are comparable to the electron Larmor radius in the dissipation region. For this regime, a combination of analytical analyses and numerical simulations demonstrate that electron orbits are sufficiently influenced by the reconnecting magnetic field component for reconnection to proceed. The very small scale lengths associated with electron Larmor radii, and the requirement to study higher order moments of the electron distribution function provide a challenge to numerical modeling of this process. We present both an overview of the underlying physical processes and a discussion of the difficulties inherent in modeling magnetic reconnection for small to moderate magnetic guide fields.