Connecting Kinetic and MHD Scales in Flows of Partially Ionized Plasma with Shocks*

Flows of partially ionized plasma are frequently characterized by the presence of both thermal and nonthermal populations of ions. Such flows cannot be modeled using traditional MHD equations and require more advanced approaches to treat them. If a non-thermal component of ions is formed due to charge exchange and collisions between the thermal ions and neutral atoms, it experiences the action of magnetic field, its distribution function is isotropized, and it soon acquires the velocity of the ambient plasma without being thermodynamically equilibrated. This situation, occurs in the outer heliosphere -- the part of interstellar space beyond the solar system whose properties are determined by the solar wind interaction with the local interstellar medium. To describe such flows we have developed a numerical model that describes the flow of plasma with MHD equations, whereas the transport of neutral atoms is modeled kinetically, by solving the corresponding Boltzmann equations. The presence of non-termal (pickup) ions (PUIs) and turbulence they generate requires their kinetic treatment at collisionless shocks. We incorporate such kinetic process intothe global MHD model of the heliosphere by imposing specifcally designed boundariy conditions at the heliospheric termination shock. We describe the model details and comapre simulation results with the IBEX, New Horizons, and Voyager data.