MICROSTRUCTURE OF THE HELIOSPHERIC TERMINATION SHOCK: IMPLICATIONS FOR ENERGETIC NEUTRAL ATOM OBSERVATIONS
- Center for Space Plasma and Aeronomic Research (CSPAR), University of Alabama in Huntsville, Huntsville, AL 35899 (United States)
- Southwest Research Institute, San Antonio, TX 78238 (United States)
The Voyager 2 plasma observations of the proton distribution function downstream of the quasi-perpendicular heliospheric termination shock (TS) showed that upstream thermal solar wind ions played little role in the shock dissipation mechanism, being essentially transmitted directly through the shock. Instead, the hot supra-thermal pickup ion (PUI) component is most likely responsible for the dissipation at the TS. Consequently, the downstream proton distribution function will be a complicated superposition of relatively cool thermal solar wind protons and hot PUIs that have experienced either direct transmission or reflection at the TS cross-shock potential. We develop a simple model for the TS microstructure that allows us to construct approximate proton distribution functions for the inner heliosheath. The distribution function models are compared to kappa-distributions, showing the correspondence between the two. Since the interpretation of energetic neutral atom (ENA) fluxes measured at 1 AU by IBEX will depend sensitively on the form of the underlying proton distribution function, we use a three-dimensional MHD-kinetic global model to model ENA spectra at 1 AU and ENA skymaps across the IBEX energy range. We consider both solar minimum and solar maximum-like global models, showing how ENA skymap structure can be related to global heliospheric structure. We suggest that the ENA spectra may allow us to probe the directly the microphysics of the TS, while the ENA skymaps reveal heliospheric structure and, at certain energies, are distinctly different during solar minimum and maximum.
- OSTI ID:
- 21392422
- Journal Information:
- Astrophysical Journal, Vol. 708, Issue 2; Other Information: DOI: 10.1088/0004-637X/708/2/1092; ISSN 0004-637X
- Country of Publication:
- United States
- Language:
- English
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Related Subjects
COSMOLOGY AND ASTRONOMY
APPROXIMATIONS
DISTRIBUTION FUNCTIONS
IONS
MAGNETOHYDRODYNAMICS
MICROSTRUCTURE
PROTONS
SHOCK WAVES
SOLAR WIND
STARS
VOYAGER SPACE PROBES
BARYONS
CALCULATION METHODS
CHARGED PARTICLES
ELEMENTARY PARTICLES
FERMIONS
FLUID MECHANICS
FUNCTIONS
HADRONS
HYDRODYNAMICS
MECHANICS
NUCLEONS
SOLAR ACTIVITY
SPACE VEHICLES
STELLAR ACTIVITY
STELLAR WINDS
VEHICLES