HR: 0830h
AN: SH31A-1095    [PDF]
TI: Observation of the lower-hybrid drift instability in a laboratory current sheet
AU: * Carter, T A
EM: tcarter@physics.ucla.edu
AF: Department of Physics and Astronomy, UCLA, 405 Hilgard Ave, Los Angeles, CA 90095-1547
AB: The exact role of turbulence in collisionless magnetic reconnection has been a controversial theoretical topic, with some theories suggesting it is essential to provide anomalous resistivity, while others present a laminar fast reconnection mechanism based on the Hall term in the generalized Ohm's law. A thorough study of fluctuations in the current sheet of the Magnetic Reconnection Experiment (MRX) was performed in order to aid in resolving this controversy. Using amplified Langmuir and magnetic probes, we have measured broadband fluctuations in the lower hybrid frequency range ($f \sim 10-15$MHz) which arise with the formation of the current sheet in MRX. The frequency spectrum, spatial amplitude profile, and spatial correlations in the measured turbulence were examined carefully, finding consistency with theories of the lower-hybrid drift instability (LHDI). The observation of the LHDI in MRX has provided the first opportunity to experimentally study its role in the process of magnetic reconnection. It was found that: (1) the LHDI amplitude does not correlate well in time or space with the reconnection electric field (which is directly related to the rate of reconnection) and (2) the LHDI amplitude was found to be fairly insensitive to collisionality, unlike the measured resistivity anomaly. These two findings suggest that the LHDI does not play an essential role in determining the reconnection rate in MRX.
DE: 7835 Magnetic reconnection
DE: 7863 Turbulence
DE: 7871 Waves and instabilities
SC: SPA - Solar and Heliospheric Physics [SH]
MN: 2003 Fall Meeting