Magnetohydrodynamic modeling of the solar wind in the outer heliosphere: Effects of pickup protons

A. V. Usmanov, M. L. Goldstein, W. H. Matthaues, and B. Breech  

We will present initial results from a three-dimensional MHD solar wind model that accounts for turbulent transport and heating of the solar wind plasma and treats the pickup protons, which are produced in the solar wind flow by the photoionization and the charge exchange with the interstellar neutral hydrogen, as a separate fluid. The model is used to simulate the global steady-state structure of the solar wind in the region from 0.3 to 100 AU. The pickup protons are assumed to be comoving with the solar wind and are described by separate mass and energy equations. Governing large-scale Reynolds-averaged equations are solved simultaneously with a set of small-scale equations for turbulence transport and dissipation. The model accounts for the energy transfer from pickup protons to solar wind protons and for the plasma heating due to turbulent dissipation. A novel feature of the present formulation is that the momentum equation contains a term that describes the loss of momentum by the solar wind flow due to the charge exchange and photoionization.