Authors: Kota J, Hsieh KC, Jokipii JR, Czechowski A, Hilchenbach M
Reference: J. GEOPHYS. RES. 106 (A11): 24907-24914 NOV 1 2001
Abstract:
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