A Three-Dimensional MHD Model of the Solar Wind with Pickup Protons

A. V. Usmanov, M. L. Goldstein, NASA/Goddard Space Flight Center, Greenbelt, MD 20771, USA

We present initial results from a three-dimensional steady-state solar wind model that accounts for the effects of pickup protons in the distant heliosphere. Inside 1 AU, we employ the model developed earlier Usmanov and Goldstein [2003] that consists of two regions: region I (1-20 solar radii) where a steady-state solution is obtained using time-relaxation, and a region II (20 solar radii - 1 AU) where the solution is constructed by integrating the governing MHD equations along radius. In the present work, we modified that model to include a region III that extends beyond 1 AU where we consider a population of interstellar pickup protons and its interaction with the solar wind protons. Following Isenberg [1986] and Whang [1998], we take into account both ionization and charge exchange for the production of pickup protons and write down the energy equations for the pickup and solar wind protons, independently. For the interstellar neutral hydrogen, we presently use a zero order approximation that assumes that the neutral hydrogen is homogeneously distributed throughout the heliosphere. We compute the global structure of the solar wind from the coronal base to the outer heliosphere and present a study of the effects of the pickup protons on solar wind structure.