Viewing corotating interaction regions globally using energetic neutral atoms

We present model simulations to estimate the flux of 25-100 keV energetic n eutral atoms (ENAs) that can be expected from charge exchange between the i on populations accelerated at corotating interaction regions and the slow n eutral atoms penetrating from the local interstellar matter. The extended s tructure of a corotating interaction region (CIR) evolving in space is a ma jor plasma feature in the inner heliosphere that contains a wealth of infor mation on shock development and charged-particle acceleration. The detectio n of energetic neutral atoms originating from CIRs, with directional, mass, and energy resolutions, is a way to view MRS remotely. This global view in ENAs may provide important information complementary to in situ particle a nd plasma and field observations. We apply a three-dimensional numerical co de to model CIRs and simulate the transport of energetic particles accelera ted at the forward and reverse shocks of the CIR. Our simulation results ar e applied to the ongoing ENA observations by the Solar and Heliospheric Obs ervatory (SOHO) and that anticipated by Cassini. We find that a CIR origin of the ENAs detected by the high suprathermal time-of-flight sensor of the charge, element, and isotope analysis system on SOHO cannot be ruled out. O ur simulations also reveal that the concentration of local interstellar He atoms focused by the Sun's gravitation contributes significantly to the pro duction of ENAs in the inner regions of the quiet heliosphere.