HR: 11:50h
AN: SH52A-06 [Abstracts]
TI: Alfven-cyclotron Scattering of Solar Wind Ions: Hybrid Simulations
AU: * Gary, S P
EM: pgary@lanl.gov
AF: Los Alamos National Laboratory, M.S. D466, Los Alamos, NM 87545
United States
AU: Yin, L
EM: lyin@lanl.gov
AF: Los Alamos National Laboratory, M.S. D466, Los Alamos, NM 87545
United States
AU: Winske, D
EM: winske@lanl.gov
AF: Los Alamos National Laboratory, M.S. D466, Los Alamos, NM 87545
United States
AB:
Cyclotron resonances are the fundamental wave-particle interaction
between ions and Alfvén-cyclotron fluctuations
at sufficiently short wavelengths and at propagation approximately
parallel or antiparallel
to a background magnetic field B_o in a relatively uniform,
collisionless plasma.
Cyclotron resonance enables pitch-angle scattering,
typically leading to changes in the perpendicular (to B_o)
energies of that species.
If alpha particles are a minority ion,
the proton and alpha resonance conditions are sensitive
functions of the alpha/proton relative speed vα p}
parallel or antiparallel to Bo.
The research described here utilizes ensembles of hybrid simulations
in which damped Alfvén-cyclotron fluctuations are imposed upon a
steady, homogeneous
plasma characterized by average solar wind parameters
near 1 AU and bearing both protons and alpha particles.
The simulations yield ion species responses to such
fluctuations as functions of three parameters:
the initial vα p/vA (where vA is the Alfvén speed),
the initial magnitude of the applied fluctuating magnetic field
energy density, and the relative density of the alphas.
For average solar wind conditions near Earth,
if magnetic power spectra extend to sufficiently short wavelengths,
saturation of alpha scattering is most likely due to exhaustion
of the fluctuating field energy density.
DE: 2471 Plasma waves and instabilities (2772)
DE: 2483 Wave/particle interactions (7867)
DE: 7829 Kinetic waves and instabilities
DE: 7867 Wave/particle interactions (2483, 6984)
SC: SPA-Solar and Heliospheric Physics [SH]
MN: Fall Meeting 2005