HR: 08:45h
AN: SM11C-04    [Abstracts]
TI: Kinetic Alfv\`en Waves and Plasma Heating and Transport at the Magnetopause
AU: * Cheng, C Z
EM: fcheng@pppl.gov
AF: Princeton University, Princeton Plasma Physics Laboratory, Princeton, NJ 08543 United States
AU: Johnson, J R
EM: jrj@pppl.gov
AF: Princeton University, Princeton Plasma Physics Laboratory, Princeton, NJ 08543 United States
AB: Large amplitude transverse ULF waves with frequencies below the ion cyclotron frequency are nearly always found at the magnetopause and they contain most of the observed wave energy. These transverse waves are consistent with kinetic Alfv\'en waves (KAWs) that are produced by mode conversion of upstream compressional MHD waves at the magnetopause. The KAW activity should be larger for southward IMF than for northward IMF conditions, which is supported by observational study of levels of ULF wave activity (amplitude and polarization) as a function of magnetic shear, Alfv\'en velocity gradient, and magnetosheath wave activity. Particle interaction with KAWs with wavelength on the order of ion gyroradii can cause perpendicular heating of ions via stochastic processes and parallel heating of electrons via Landau damping. Moreover, particle interaction with KAWs causes significant magnetosheath particle transport across the magnetopause with a diffusion coefficient $D \sim 10^9 \rm m^2/s$, which is sufficient to maintain the observed density gradient across the magnetopause. Because large amplitude transverse ULF waves are nearly always found at the magnetopause, the wave-particle interaction process is inevitable, and we expect a continuous mixing in energy spectra of magnetosheath and magnetospheric particles in the LLBL. Although the magnetic reconnection process would predict a similar particle transport rate via direct entry along reconnected field lines, it predicts substantially different energy spectra in LLBL with two distinct particle components of magnetosheath and magnetospheric origins: the magnetosheath ions will have velocities on the order of Alfv\`en velocity and electrons form beam-like distributions. The difference in particle energy spectra should be useful for devising experimental tests that can distinguish the direct particle entry due to reconnection from the diffusive particle entry due to wave-particle interaction.
DE: 7827 Kinetic and MHD theory
DE: 7859 Transport processes
DE: 7867 Wave/particle interactions
DE: 2724 Magnetopause, cusp, and boundary layers
SC: SPA-Magnetospheric Physics [SM]
MN: 2004 AGU Fall Meeting