SPRG Seminars
April 9, 2013:
"Proton Heating by Pick-up-generated Waves in the Expanding Solar Wind: Hybrid Simulations"
Pavel Travnicek, Space Science Laboratory, University of California at Berkeley
Proton energization observed in the outer heliosphere by Voyager 2 can be attributed to the dissipation of the wave energy generated by pick-up protons. Results from one-dimensional self-consistent kinetic simulation of this kinetic phenomenon using the hybrid expanding box (HEB) model will be presented. In this simulation the magnetic field is assumed to be strictly transverse and the plasma does not contain any pick-up protons initially but they are injected continuously during the expansion assuming a simple model for the charge-exchange process. The injected pick-up protons form a ring velocity distribution function in the solar wind which becomes eventually unstable and generates cyclotron waves which scatter the pick-up ions forming a shell distribution function. The generated waves also heat the solar wind protons and this cyclotron heating is able to overcome the adiabatic cooling in agreement with the Voyager 2 observations. We discuss constraints imposed by the dimensionality of the solution not allowing oblique wave modes to propagate. We propose additional one dimensional and more complex two-dimensional simulation runs.