Self-consistent hybrid simulations of the interaction of the heliosphere with the local interstellar medium

A new method for investigating the interaction of the solar wind with the p artially ionized local interstellar medium (LISM) is presented. The solar w ind and the interstellar plasma are modeled using a two-dimensional (2-D) h ydrodynamic numerical code. The plasma is coupled to the neutral hydrogen ( of both interstellar and solar wind origin) via resonant charge exchange, T o model the neutral H distribution, we use a nonstationary 2.5-D particle m esh method to solve the Boltzmann equation, which is coupled self-consisten tly to the interstellar and solar wind plasma. Numerical self-consistency i s achieved by iterating the plasma and neutral H distributions between the two numerical schemes until a steady state is achieved. Results from three test applications are presented and discussed, including the first one-shoc k kinetic simulation. The simulations are able to reproduce the main featur es of the heliosphere such as shock structure, hydrogen wall, and heating, deceleration and filtration of neutral hydrogen. In addition, they enable t he study and interpretation of the non-Maxwellian hydrogen distribution fun ction. Traces of fast neutrals originating inside the termination shock and the heliosheath/heliotail region can be found far upstream of the outer he liosphere. The influence of different interstellar plasma boundary values o n the heliosphere is highlighted in the comparison of two supersonic simula tions and one subsonic simulation. In particular, by comparing the simulate d energetic neutral atom (ENA) fluxes at 1 AU of the supersonic and subsoni c models, it is found that the subsonic flux is significantly underabundant in the energy range 10 - 60 eV compared to the supersonic case. This may o ffer an important diagnostic for determining whether the heliosphere posses ses a bow shock or not.