Weak turbulence cascading effects in the acceleration and heating of ions in the solar wind

Abstract

We study the wave-particle interaction and the evolution of electromagnetic waves propagating through a solar-wind-like plasma composed of cold electrons, isotropic protons, and a small portion of drifting anisotropic He+2 (T α = 6 T α) and O+6 (T O = 11 T O ) ions as suggested in Gomberoff & Valdivia and Gomberoff et al., using two approaches. First, we use quasilinear kinetic theory to study the energy transfer between waves and particles, with the subsequent acceleration and heating of ions. Second, 1.5 D (one spatial dimension and three dimensions in velocity space) hybrid numerical simulations are performed to investigate the fully nonlinear evolution of this wave-particle interaction. Numerical results of both approaches show that the temperatures of all species evolve anisotropically, consistent with the time-dependent wave-spectrum energy. In a cascade effect, we observe the emergence of modes at frequencies higher than those initially considered, peaking at values close to the resonance frequencies of O+6 ions (ω ∼ ΩCO) and He+2 ions (ω ∼ Ωcα), being the peak due to O+6 ions about three times bigger than the peak associated with He+2 ions. Both the heating of the plasma and the energy cascade were more efficient in the nonlinear analysis than in the quasilinear one. These results suggest that this energy cascade mechanism may participate in the acceleration and heating of the solar wind plasma close to the Sun during fast streams associated with coronal holes. © 2014. The American Astronomical Society. All rights reserved.