Alfven-cyclotron scattering of solar wind ions: Hybrid simulations

[ 1] This paper describes results from ensembles of hybrid simulations of steady, homogeneous, collisionless plasmas characterized by average solar wind parameters near 1 AU upon which damped, resonant Alfven-cyclotron fluctuations are imposed. The applied fluctuations propagate parallel to the background magnetic field B-o. The ensembles yield late-time proton and alpha particle responses to such fluctuations as functions of the initial magnitude of the applied fluctuating magnetic field energy and the initial nu(alpha p)/nu(A) ( where nu(alpha p) is the alpha/proton relative speed and nu(A) is the Alfven speed). The simulations show a strong, consistent negative correlation between the alpha temperature anisotropy T-perpendicular to alpha/ T-parallel to alpha ( where the directional subscripts refer to directions perpendicular and parallel to B-o) and nu(alpha p)/nu(A). On average the simulations also show a weaker, positive correlation between the proton temperature anisotropy and nu(alpha p)/nu(A). Both correlations are in agreement with statistical observations from the solar wind near 1 AU, thereby confirming earlier conclusions that such observations are signatures of Alfven-cyclotron scattering of ions in the solar wind.