Pickup ion acceleration at the termination shock at multiple locations

Abstract:

We estimate the intensity of accelerated pickup ions at various locations along the termination shock using a combination of 2D hybrid simulations, solar-wind and pickup-ion modeling, large-scale shape of the termination shock, and Voyager observations. We estimate the solar wind, pickup-ion, and magnetic field parameters just upstream of the termination shock at various locations, including the flanks, downwind (or tail-ward) direction, and the poles, using a solar-wind/pickup-ion/turbulence model. This model solves for the transport of pickup ions which also generate solar-wind and magnetic field turbulence that, in turn, heat the pickup ions and solar wind. The model gives predictions for the solar wind, pickup ions, and magnetic field parameters as a function of space. We also use predictions from a large-scale model of the blunt-shaped termination shock to estimate the unit normal to the shock surface at various locations. Using these upstream parameters, we utilize the self-consistent, two-dimensional hybrid simulation to study the evolution of the pickup ions across the termination shock, including their acceleration to energies exceeding 50-100 keV. The simulation is limited in size, and, thus cannot attain higher energies than these, but presumably this is sufficient to study the origin of the high-energy tail of the distribution which form the low-energy portion of the anomalous cosmic ray spectrum. The results from our estimates have implications for the NASA IBEX mission, the upcoming NASA/ IMAP mission as well as modeling of anomalous cosmic rays and comparison with Voyager observations. This project is part of NASAs DRIVE Center SHIELD.