HR: 14:55h
AN: NG33A-06    [Abstracts]
TI: Electron energization by field line annihilation in whistler spheromaks
AU: * Stenzel, R L
EM: stenzel@physics.ucla.edu
AF: Department of Physics and Astronomy, UCLA, Box 951547, Los Angeles, CA 90095-1547, United States
AU: Urrutia, J M
AF: Department of Physics and Astronomy, UCLA, Box 951547, Los Angeles, CA 90095-1547, United States
AU: Strohmaier, K D
AF: Department of Physics and Astronomy, UCLA, Box 951547, Los Angeles, CA 90095-1547, United States
AB: A loop antenna is inserted into a large laboratory plasma with its axis along the dc magnetic field. A large oscillating loop current is applied which in one polarity produces a field-reversed configuration, in the other a strong mirror field. This arrangement excites nonlinear whistler modes with topologies alternating each half cycle between that of a spheromak and a mirror [http://link.aps.org/abstract/PRL/v96/e095004/html]. The propagation speed and damping of whistler spheromaks and whistler mirrors are amplitude dependent. In whistler spheromaks, electrons are strongly accelerated along the toroidal magnetic null line (separator), resulting in magnetic energy loss by field line annihilation at the O-point. In whistler mirrors, electrons perform \mathbf{E} × \mathbf{B} drifts, hence are not energized. Wave-wave interactions also differ: Counter-propagating mirrors pass through each other without interaction, whistler spheromaks collide inelastically and merge into stationary field-reversed configuration. These nonlinear properties are important for understanding strong whistler turbulence, fast reconnection, and whistler wave excitation from loop antennas. Work supported by NSF/DOE.
DE: 2772 Plasma waves and instabilities (2471)
DE: 7839 Nonlinear phenomena (4400, 6944)
DE: 7867 Wave/particle interactions (2483, 6984)
SC: Nonlinear Geophysics [NG]
MN: 2007 Fall Meeting