THE COSMIC-RAYS MEDIATED NONPOLYTROPIC SOLAR-WIND INTERACTING WITH THE INTERSTELLAR NEUTRAL MATTER

The solar wind spherical flow is considered under the combined action of gas pressure, magnetic field pressure and pressures of cosmic rays; both galactic and anomalous component. The interaction of solar wind ions with LISM neutrals is taken into account self-consistently by int roducing the appropriate source terms in the flow equations. The numer ical solutions of a set of five differential equations describing the system, obtained for different model parameters, provide a spectrum of possible configurations of the outer heliosphere. The formation of th e solar wind termination shock is described and the shock position and strength are studied. The nonpolytropic solar wind is considered; the difference between the calculated pressure and the one resulting from the polytropic law are discussed. While taking into account the effec ts connected with the production of superthermal population leads to a n increase of the shock compression ratio, the interaction with the LI SM neutrals results in weaker shocks. The galactic cosmic rays push th e shock inward, the anomalous component cosmic rays move it outward. S everal sets of input parameters such as the initial speed and density of the solar wind (fast or slow), the cosmic ray diffusion coefficient s, the density of interstellar neutrals, and the efficiency of the cos mic ray production at the shock are considered. For a typical distance to the solar wind termination shock of 60-100 AU, the efficiency of t he cosmic rays production must be in the range 0-15%, in order to obta in well-behaved solutions in the downwind region.