HR: 0800h
AN: SM51A-1284    [Abstracts]
TI: Magnetic Field Topology of a Tilted Current Ring in a Uniform Magnetoplasma
AU: * Strohmaier, K D
EM: kyle@physics.ucla.edu
AF: Department of Physics and Astronomy, UCLA, Box 951547, Los Angeles, CA 90095-1547 United States
AU: Urrutia, J
SM51A-1284 AF: Department of Physics and Astronomy, UCLA, Box 951547, Los Angeles, CA 90095-1547 United States
AU: Stenzel, R L
SM51A-1284 AF: Department of Physics and Astronomy, UCLA, Box 951547, Los Angeles, CA 90095-1547 United States
AB: An electron current ring has been induced with a pulsed magnetic loop antenna in a large, uniform and magnetized laboratory plasma. The parameter regime is that of electron MHD (magnetized electrons, unmagnetized ions). The current ring is primarily produced by electron Hall currents. After the end of the pulsed antenna current, the induced electron current relaxes self-consistently free of boundary effects. Time and 3-D space-resolved field measurements have been performed with magnetic probes. These revealed that the toroidal current ring initially tilts and then splits into two rings which gradually separate. The field topology changes during the relaxation: Initially, it is a field-reversed configuration with two 3-D radial null points on axis and a 2-D toroidal null line in the current ring, (analogous to a Hills vortex). The tilt degenerates the toroidal null line into two 3-D spiral null points. The separatrix surface is no longer a closed, symmetric shell. Formerly closed field lines connect through the spiral nulls with open lines. The topology change implies reconnection in a 3-D topology. During the relaxation, magnetic energy is dissipated. Electron heating occurs in the toroidal current layer with the spiral nulls, but not in the radial nulls. The dynamics of the current ring (splitting and separation) is a propagation phenomenon and is not controlled by magnetic forces as in MHD. Work supported by the Air Force Research Laboratory.
DE: 2487 Wave propagation (0689, 3285, 4275, 4455, 6934)
DE: 2723 Magnetic reconnection (7526, 7835)
DE: 2772 Plasma waves and instabilities (2471)
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005