Nonextensive effects on the quasi-linear heating of ions in the solar wind

The problem of the heating of solar wind plasma has received special attention during the last decades. Recent observations and theoretical results seem to indicate that most of the acceleration process occurs within a few solar radii from the Sun and the main mechanism is due to resonant absorption of ion-cyclotron waves. However, the detailed processes for the energy transfer between waves and different particle species is still an open question. To address these issues, we investigate the wave-particle interaction and evolution of circularly polarized electromagnetic waves propagating in a magnetized plasma. Previous works show the presence of high energy tails in the particle velocity distribution function (VDF) in interplanetary systems, that correspond to a family of specific power-law distributions. In fact, the observed non-Maxwellian shapes has been found to be consistent with nonextensive formalisms. Here we investigate how the shape of the VDF is modified in the solar wind, through a quasi-linear theory of the energy transfer between ions and waves, with the subsequent heating of the particles, by considering a nonrelativistic VDF which maximizes the nonextensive Tsallis entropy with temperature anisotropy. This system is analyzed for several values of the nonextensive parameter q, and compared with results using the extensive Boltzmann-Gibbs formalism.