HR: 0800h
AN: SM51A-1282    [Abstracts]
TI: Properties of Whistler Waves With Magnetic Fields Exceeding the Ambient Field
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
SM51A-1282 AF: Department of Physics and Astronomy, UCLA, Box 951547, Los Angeles, CA 90095-1547 United States
AU: Strohmaier, K D
SM51A-1282 AF: Department of Physics and Astronomy, UCLA, Box 951547, Los Angeles, CA 90095-1547 United States
AB: In a large laboratory plasma nonlinear whistler waves are excited and their propagation characteristics measured with magnetic probes. The nonlinearity arises from the wave magnetic field which can exceed the ambient magnetic field. Since the whistler wave dispersion depends on the total magnetic field, the wave properties thus become amplitude-dependent. The waves are excited with a magnetic loop antenna whose axis is parallel to the uniform dc background magnetic field. Such antennas excite spatial wave packets which propagate predominantly along the ambient dc magnetic field. Fourier analysis shows that the wave packets consists of a superposition of oblique low-frequency whistler modes. The propagation speed is observed to depend on wave amplitude and polarity: When the parallel wave magnetic field adds to the ambient field, the net field is increased and the wave propagates faster than a small-amplitude whistler wave. When the wave magnetic field opposes the ambient field, the wave slows down and becomes evanescent at the magnetic null point. Magnetic energy is trapped between two radial magnetic null points and much of it is dissipated into electron heating. The dynamics of the distorted wave packets as well as the topology of the 3-D null points and separatrices will be shown. 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