Galactic cosmic-ray modulation near the heliopause

Journal Article · Sat Sep 20 00:00:00 EDT 2014 · Astrophysical Journal

DOI:https://doi.org/10.1088/0004-637X/793/1/18· OSTI ID:22365042

Guo, X.; Florinski, V. ^[1]

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1. Center for Space Plasma and Aeronomic Research, University of Alabama, Huntsville, AL 35899 (United States)

We investigate the modulation of galactic cosmic rays in the inner and outer heliosheaths using three-dimensional numerical simulations. The model is based on the Parker transport equation integrated using a stochastic phase-space trajectory method. Integration is performed on a plasma background obtained from a global three-dimensional magnetohydrodynamic simulations. Our results predict a negligible amount of modulation in the outer heliosheath because of weak scattering of cosmic ray ions owing to very low levels of magnetic fluctuation power at wavenumbers relevant to the transport of cosmic rays with MeV to GeV energies. This means that the heliopause may be treated as a Dirichlet-type boundary for the purpose of energetic particle modeling. We present models with and without drift velocity to facilitate comparison with papers published earlier. We also attempt to reproduce the sudden step-like increases of cosmic-ray intensity observed by Voyager 1 before its encounter with the heliopause. Our results indicate that very slow cross-field diffusion in the outer heliosheath could produce a large gradient of cosmic rays inside the heliospheric boundary. The resulting large gradient in cosmic-ray intensity near the heliopause qualitatively agrees with recent Voyager 1 observations.

• OSTI ID: 22365042
• Journal Information: Astrophysical Journal, Vol. 793, Issue 1; Other Information: Country of input: International Atomic Energy Agency (IAEA); ISSN 0004-637X
• Country of Publication: United States
• Language: English

Related Subjects

79 ASTROPHYSICS
COSMOLOGY AND ASTRONOMY
COMPUTERIZED SIMULATION
COSMIC RADIATION
DIFFUSION
DIRICHLET PROBLEM
FLUCTUATIONS
GEV RANGE
HELIOSPHERE
MAGNETIC FIELDS
MAGNETOHYDRODYNAMICS
MEV RANGE
MODULATION
PHASE SPACE
PLASMA
SCATTERING
STOCHASTIC PROCESSES
SUN
THREE-DIMENSIONAL CALCULATIONS
TRANSPORT THEORY
TURBULENCE
VOYAGER SPACE PROBES