March 22, 2013, 12:00 pm - 1:00 pm

March 22, 12:00 pm - 1:00 pm

Heating of protons and alpha particles by dispersive Alfven-cyclotron waves -- 2.5D hybrid simulations

Yana Maneva, NASA/GSFC and CUA

We perform 2.5D hybrid simulations to model the preferential heating and differential acceleration of minor ions as observed by remote sensing in coronal holes and measured in situ in the fast solar wind at various heliospheric distances. We consider a low-beta plasma consisting of fluid electrons, particle-in-cell protons and He++ ions and different spectra of parallel propagating Alfven-cyclotron waves as initial energy source for the ion heating and acceleration. For fixed low wave-numbers the generated wave spectrum in a multi-species plasma generally shifts towards higher frequencies. This effect is further enhanced when differential streaming is present as indicated by remote sensing of coronal holes and observed in situ in the fast solar wind. We use the results from the cold plasma linear theory to initialize the nonlinear 2.5D hybrid simulations and compare the resulting ion heating, temperature anisotropies and differential streaming when the initial wave spectra belongs to the alpha-cyclotron with and without initial relative drifts, and study the nonlinear 2D effects, extending our previous 1D hybrid studies. Finally, we investigate the effect of a gradual solar wind expansion, consider its influence on the wave-particle interactions and discuss its implications for the non-adiabatic perpendicular cooling for both ion species.