Date : 4/12 (Thu) [14:30 - ] @F620
Speaker: Dr. Fulvia Pucci (NIFS/Princeton)
Title : Magnetic reconnection at kinetic scales: from the trigger mechanism at ion scales to electron energization
Abstract: Magnetic reconnection is thought to be responsible for flares, CMEs and explosive events in astrophysical as well as in laboratory plasmas. One of the main questions in reconnection research concerns how this mechanism may account for fast magnetic energy conversion to kinetic and thermal energies. I will first recall the concept of "ideal" tearing and discuss resistive as well as collisionless reconnection, generalizing the trigger concept to include the Hall as well as electron inertia effects. I will then discuss fundamental implications of this model and possible future applications to study the number of islands and the generalization to the fractal model. Electron dynamics is key to magnetic field dissipation in collisionless reconnection. In 2D reconnection, the main mechanism that limits the current density and provides an effective resistivity is the electron pressure tensor term, that has been shown to break the frozen-in condition at the x-point. In addition the electron-meandering-orbit scale controls the width of the electron dissipation region around the reconnection region, where the electron temperature is observed to increase both in recent MMS observations as well as in laboratory experiments (MRX). By means of two-dimensional, full-particle simulations in an open system, we investigate how the energy conversion and particle energization depends on the guide field intensity. We compare our results with observations using the present catalogue of MMS diffusion region crossings. We finally investigate the electron distribution functions as well as particle orbits in the electron diffusion region and the exhaust, in order to clarify preferential electron heating/acceleration in two-dimensional systems.
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