HR: 0800h
AN: SH21A-0299    [Abstracts]
TI: Neutral Effects on Alfvén Wave Propagation and the Effect on Coronal Heating
AU: Kelly, R
EM: rkelly@ece.unm.edu
AF: University of New Mexico, ECE Dept., MSC01-1100, Albuquerque, NM 87131,
AU: * Watts, C
EM: cwatts@ece.unm.edu
AF: University of New Mexico, ECE Dept., MSC01-1100, Albuquerque, NM 87131,
AU: Hanna, J X
EM: jhanna@ucsd.edu
AF: UC San Diego, Physics Dept., La Jolla, CA 92093,
AB: Alfvén waves are ubiquitous in space plasmas, influencing the dynamics of, for example, solar flares and magnetospheric reconnection. In particular, Alfvén waves are considered as one candidate for the heating of the solar transition region and corona. Importantly, because both the chromosphere and transition regions are dominated by neutral gas, Alfvén wave interaction with neutral particles may be important in this heating process. To better understand the effect of neutrals on Alfvén waves we have undertaken a program to study these waves in the laboratory. We present results from both the HelCat and the ALESPI devices. The HelCat (Helicon-Cathode) device is 4 m long, with a 0.5 m diameter using both helicon and cathode plasma sources; ALESPI (Auburn Linear Experiment for Space Plasma Studies) is a 2 m helicon device. The high density steady-state, current-free plasma allows detailed study of both shear and compressional waves with a varying neutral fraction. We launch shear waves with an asymmetric exciter. Depending on this neutral fraction, the measured dispersion curve changes dramatically. We observe propagation above the ion cyclotron frequency ω _ci, the nominal cutoff for shear waves. However, theoretical models show that the propagating wave is dominated by shear waves with both m=0 and higher order mode components due to the asymmetry of the launching scheme, which accounts for the observed propagation above ω _ci.
DE: 6984 Waves in plasma (7867)
DE: 7507 Chromosphere
DE: 7546 Transition region
DE: 7836 MHD waves and instabilities (2149, 2752, 6050)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: 2007 Fall Meeting