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New Frontiers in Collisionless Reconnection: Exploring Magnetosphere-Relevant Reconnection with Experiments and Custom Kinetic Simulations
Date: Friday, December 9th
Time: 1:00 pm - 12:00 pm
Place: B343 Sterling or
Speaker: Samuel Greess, Physics Graduate Student
Abstract: Magnetic reconnection is a ubiquitous phenomenon throughout the universe, but in terms of proximity, its occurrence at the day-side magnetopause is the instance that is closest to Earth both spatially and in importance to human life. At the day-side magnetopause, the solar magnetic field reconnects with the magnetic field of the Earth, beginning the process that results in the transfer of energized solar wind particles into the Earth's upper atmosphere. Usually, the result of these incursions is only the ethereal beauty of the auroras (borealis and australis); however, larger quantities of incident plasma can and have had devastating effects on terrestrial and space-based electronic systems. Predicting these geomagnetic storm events depends on an understanding of both how and when large quantities of plasma are emitted from the Sun (also a reconnection-based event) and how long it will take for these particles to enter the Earth's atmosphere via the magnetopause reconnection process. To that end, in addition to satellite missions created to measure the in situ process, experiments and simulations here on Earth are studying reconnection in the relevant parameter regimes, particularly in plasmas whose collisionality is low enough to mimic the space environment. One such experiment is the Terrestrial Reconnection EXperiment (TREX), which is based as the University of Wisconsin-Madison as a partner of the Wisconsin Plasma Physics Laboratory (WiPPL) collaborative research facility. TREX is designed to access the kinetic regime, which is typified by thin current layers, anisotropic pressure distributions, and fast reconnection. In conjunction with TREX, the newly developed Cylindrical VPIC (Vectorized Particle-in-Cell) code from Los Alamos National Laboratory has been used to simulate TREX in manner that preserves the experiment's cylindrical symmetry while optimizing computational efficiency. Different modified versions of the basic TREX VPIC setup have been successfully used to confirm and complement experimental findings, as well as to investigate plasma regimes the experiment cannot (presently) reach and to model different proposed TREX drive coil geometries. This thesis will present work from both the TREX laboratory and TREX VPIC simulations, with an emphasis on comparing the measured properties of reconnection in both scenarios and demonstrating how these data align with theoretical predictions about the kinetic reconnection parameter regime. Significant background to the construction and operation of TREX, Cylindrical VPIC, and relevant portions of the WiPPL facility will also be included.
Host: Jan Egedal
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