Effect of interstellar neutral hydrogen on the termination of the solar wind

The effect of interstellar hydrogen penetrating the supersonic solar wind region from the boundary shell is considered. The density of neutral hydrogen is taken to be one particle per cubic centimeter in interstellar space and the density in the supersonic solar wind region is attenuated by a factor exp(-9a/r) at a distance r from the sun. A set of flow equations is obtained in a manner similar to that of Biermann et. al. for the solar wind-comet problem. The exchange of mass, momentum, and energy due to photoionization and charge exchange are included with appropriate source terms and the equations are solved numerically to find the flow velocity of the solar wind. The solar wind velocity is seen to drop by an order of magnitude from one to 100 a.u. neglecting the magnetic field pressure of the interstellar medium and setting M(mach number) = 1 in the flow equations gives a value for the radius of the supersonic solar wind region of about 50 a.u. The radius of the solar wind region is also calculated using the momentum, balance method. It is seen that the radius of the supersonic solar wind region is dependent on the thiolmess of the boundary shell and the pressure profile. It is shown that if a"uniform neutral hydrogen density of one particle per cubic centimeter is assumed, the radius of the supersonic solar wind region increases over the value given above. This peculiar result is attributed to the nonlinearity of the flow equations.