HR: 1340h
AN: SM23B-0422    [Abstracts]
TI: High frequency waves in a current sheet
AU: * Gekelman, W
EM: geelman@physics.ucla.edu
AF: UCLA Department of Physics and Astronomy, 1000 Veteran Avenue Rm 15-70, Los Angeles, CA 90095-1696 United States
AU: Pribyl, P
EM: pribyl@ucla.edu
AF: UCLA Department of Physics and Astronomy, 1000 Veteran Avenue Rm 15-70, Los Angeles, CA 90095-1696 United States
AU: Vincena, S
EM: vincena@physics.ucla.edu
AF: UCLA Department of Physics and Astronomy, 1000 Veteran Avenue Rm 15-70, Los Angeles, CA 90095-1696 United States
AU: Chiang, F
EM: franklin.c.chaing.ucla.edu
AF: UCLA Department of Electrical Engineering, 405 Hilgard Avenue, Los Angeles, CA 90095-1696 United States
AB: Current sheets occur in a large variety of situations in both space and laboratory plasmas. Intense currents can disturb the local plasma parameters such as density, temperature and flow. These, in turn, can trigger low frequency waves as described in the companion talk by Vincena et al. The current sheet is embedded in a magnetoplasma and is as thick as an ion gyroradius. ( δ ≤ r_ci, B_O=750G, f_ce=2.1GHz.) Using Debye scale size probes (which can measure the electrostatic part of the electric field, E=-∇ φ, wave bursts in the whistler and electron cyclotron regimes have been identified. In dense (n_e≈ 10¹²cm^-3) laboratory plasmas investigation of Debye scale structures is non-trivial. The probes, square pads 2 microns on a side and spaced 20 microns apart (15μm ≤ λ_d ≤ 30μm) were grown using MEMs techniques. The probes are oriented along and transverse to the ambient magnetic field. Amplifiers ( f ≤ 2 GHz) are positioned less than a centimeter from the probe tips as the charge involved with detected signal is less than 100 pC. The signals were acquired with an oscilloscope with a 8GHz analog bandwidth and a sampling rate as high as 20 GHz. The scope had enough memory in each channel that both the low frequency (f≈ 30kHz) and high frequency phenomena could be recorded in the same time series. The character of the signals is markedly different inside and outside of the current sheet. It also differs across and along the ambient magnetic field. Wavelet analysis clearly shows the bursty nature of the transverse wave electric field. Statistics of the high frequency waves, their universality and relation to the low frequency phenomena in magnetized current sheets will be discussed.
DE: 2427 Ionosphere/atmosphere interactions (0335)
DE: 2435 Ionospheric disturbances
DE: 3304 Atmospheric electricity
DE: 3324 Lightning
SC: SPA-Magnetospheric Physics [SM]
MN: Fall Meeting 2005