Authors: Kota J, Hsieh KC, Jokipii JR, Czechowski A, Hilchenbach M
Reference: J. GEOPHYS. RES. 106 (A11): 24907-24914 NOV 1 2001
We present model simulations to estimate the flux of 25-100 keV energetic neutral atoms (ENAs) that can be expected from charge exchange between the ion populations accelerated at corotating interaction regions and the slow neutral atoms penetrating from the local interstellar matter. The extended structure of a corotating interaction region (CIR) evolving in space is a major plasma feature in the inner heliosphere that contains a wealth of information on shock development and charged-particle acceleration. The detection 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 and plasma and field observations. We apply a three-dimensional numerical code to model CIRs and simulate the transport of energetic particles accelerated at the forward and reverse shocks of the CIR. Our simulation results are applied to the ongoing ENA observations by the Solar and Heliospheric Observatory (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. Our simulations also reveal that the concentration of local interstellar He atoms focused by the Sun's gravitation contributes significantly to the production of ENAs in the inner regions of the quiet heliosphere.
Keywords: LOCAL INTERSTELLAR-MEDIUM, CURRENT-SHEET, HYDROGEN-ATOMS, COSMIC-RAYS, HELIOSPHERE, WIND, PARTICLES, ULYSSES, CIR, ASYMMETRY