Neutral atom transport from the termination shock to 1 AU

Dynamics of H, D, and heavy Energetic Neutral Atoms (ENA) between the termination shock and 1 AU is discussed in the context of the forthcoming NASA SMEX mission IBEX. In particular, effects of the velocity-dependent radiation pressure on atomic trajectories are considered and ionization losses between TS and 1 AU are studied. It is shown, among others, that most of the dynamical effects and ionization losses are induced within a few AU from the Sun, which translates to the time domain into $\sim 1 - 3$ solar rotations before detection. This loosens considerably time requirements for tracking the ionization and radiation pressure history to just prior 3 months. ENA seem excellent tracers of the processes within the heliospheric interface, with the transport effects between the termination shock and detector relatively mild and easy to account for.Comment: submitted to Proceedings of the 5-th IGPP Astrophysics Conference, Honolulu HI, March 2006; 6 page

A kinetic control of the heliospheric interface hydrodynamics of charge-exchanging fluids

It is well known that the Solar System is presently moving through a partially ionized local interstellar medium. This gives rise to a counter-flow situation requiring a consistent description of behaviour of the two fluids -- ions and neutral atoms -- which are dynamically coupled by mutual charge exchange processes. Solutions to this problem have been offered in the literature, all relying on the assumption that the proton fluid, even under evidently nonequilibrium conditions, can be expected to stay in a highly-relaxated distribution function given by mono-Maxwellians shifted by the local proton bulk velocity. Here we check the validity of this assumption, calculating on the basis of a Boltzmann-kinetic approach the actually occurring deviations. As we show, especially for low degrees of ionization, $\xi \le 0.3$, both the H-atoms and protons involved do generate in the heliospheric interface clearly pronounced deviations from shifted Maxwellians with asymmetrically shaped distribution functions giving rise to non-convective transport processes and heat conduction flows. Also in the inner heliosheath region and in the heliotail deviations of the proton distribution from the hydrodynamic one must be expected. This sheds new light on the correctness of current calculations of H-atom distribution functions prevailing in the inner heliosphere and also of the Lyman-$\alpha$ absorption features in stellar spectra due to the presence of the hydrogen wall atoms. Deviations from LTE-functions would be even more pronounced in magnetic interfaces, which via CGL-effects cause temperature anisotropies to arise.Comment: 18 pages, 8 figures, A&A in pres