HR: 0800h
AN: SM11A-0321    [Abstracts]
TI: Signatures of Resonant Mode Conversion at the Magnetopause
AU: * Johnson, J R
EM: jrj@pppl.gov
AF: Princeton University, Plasma Physics Laboratory, PO Box 451, Princeton, NJ 08543, United States
AU: Lin, Y
EM: yliln@physics.auburn.edu
AF: Auburn University, Physics Department, Auburn, AL 36849, United States
AB: At low frequency, the MHD equations describe coupling between the compressional and Alfvén wave near the Alfvén resonance. Coupling between the modes occurs when there is a gradient in the Alfvén velocity at the location where the wave frequency matches the Alfvén resonant frequency (k_\parallel V_A). However, the modes are coupled only in the case where there is a wave perturbation (k_y) perpendicular to the magnetic field (z) and to the direction of the Alfven velocity gradient (x). At higher frequency, f > 0.1 f_ci) coupling may also occur due to the polarization drift. We solve the full fluid wave equations for a 1D magnetopause equilibrium model to determine the efficiency of mode conversion including coupling due to (f/f_ci) effects and k_y. Wave absorption is quantified by comparing the incoming and reflected compressional wave Poynting fluxes for numerical solutions obtained by solving the corresponding difference equation on a grid with appropriate boundary conditions. For the magnetopause equilibrium model, we find that mode conversion efficient peaks where (k_y V_A/ ω) ~ 0.4 and f/f_ci ~ 0.3 with nearly total absorption. The efficiency is significantly weaker (10%) in the limit f \ll f_ci as in the MHD approach. We also discuss the effect of heavy ions on the mode conversion process. We compare the mode conversion efficiency with hybrid simulations and discuss kinetic effects on the mode conversion process. Finally, we consider these results in the context of magnetopause wave measurements and discuss implications for particle transport.
UR: http://w3.pppl.gov/~jrj/magnetopause.html
DE: 2724 Magnetopause and boundary layers
DE: 2728 Magnetosheath
DE: 2772 Plasma waves and instabilities (2471)
DE: 7846 Plasma energization
DE: 7859 Transport processes
SC: SPA-Magnetospheric Physics [SM]
MN: 2007 Fall Meeting