Solar-wind acceleration by energetic particles

We present results from a two-fluid model of win the solar wind which includes the thermal gas and a nonthermal particle population. Low-energy solar cosmic rays (10 to 100 keV) can help accelerate the wind by transferring some of their momentum to comoving magnetic irregularities. We find that increases in the wind velocity of the order of 100 km/s are not uncommon when a small amount (approximately 0.01 of the total pressure at the Sun) of cosmic rays is added in the solar corona. We discuss possible cosmic ray spectra and interplanetary diffusion ranges necessary to produce this effect. Cosmic ray spectra obtained from our model are consistent with experimental data at the 1 AU distance.