Unraveling the heliosphere using ENA data and computational models

Despite the success of the Voyager mission, whose twin spacecraft have crossed the heliospheric termination shock and are on their way to the heliopause, most of the heliospheric interface remains beyond reach. The method of remote sensing of the distant heliopshere using energetic neutral atoms (ENA's) has recently gained popularity. ENA's are created when an interstellar neutral atom (predominantly Hydrogen) charge-exchanges with a proton from the sub-sonic solar wind. The resulting H-atom has the velocity of the proton, but is no longer constrained by electric or magnetic fields and can travel large distances across the heliosphere before a secondary collisional encounter. Several missions have detected these heliospheric ENAs, and the recently launched IBEX mission is dedicated solely to ENA detection. To deconvolve the heliospheric proton distribution and to estimate heliospheric structure implied by ENA observations, it is useful to look at global computational models of the heliosphere for a variety of boundary conditions. I will present the latest results of our 3D model of the heliospheric interface which couples an MHD approach for the ionized component to a kinetic description of neutral Hydrogen. By self-consistent including a non-Maxwellian distribution function for heliospheric protons, we are able to approximate the effects of pick-up ions and the resulting suprathermal ENAs into our model.