Numerical modeling of the 22-year variation of the cosmic ray intensity and anisotropy

Journal Article · Wed Jan 01 04:00:00 EST 1986 · J. Geophys. Res.; (United States)

DOI:https://doi.org/10.1029/JA091iA01p00001· OSTI ID:6329421

Kadokura, A; Nishida, A

We have solved the two-dimensional time-dependent diffusion-convection equation numerically to obtain the distribution and anisotropy of cosmic rays in the heliosphere. We have assumed that the parallel and perpendicular mean free paths are proportional to the particle Larmor radius, and we have treated each proportionality constant (a,b) as a parameter. We have found that the set (a,b) = (4,2) gives the steady state solution compatible with observations on the intensity and the solar diurnal anisotropy of cosmic rays in 0.5- to 10-GeV range as obtained at the earth. This set of (a,b) corresponds to the ratio of the diffusion coefficients D/sub parallel//D/sub perpendicular/ = 10. In our solution the intensity for the (pre-1980) interplanetary magnetic field (IMF) state where the solar magnetic dipole and the angular velocity vector are parallel is higher than for the (post-1980) state where they are antiparallel, while the phase of the diurnal anisotropy is about 15 hours for the parallel state and about 18 hours for the antiparallel state. We have also reproduced the observed small radial gradient for each IMF state. We discuss the nature of the solution in order to understand the effect of the density gradient drift motion on the cosmic ray distribution.

• Research Organization: Institute of Space and Astronautical Science, Komaba, Meguro, Tokyo, Japan
• OSTI ID: 6329421
• Journal Information: J. Geophys. Res.; (United States), Journal Name: J. Geophys. Res.; (United States) Vol. 91:A1; ISSN JGREA
• Country of Publication: United States
• Language: English

Related Subjects

640101* -- Astrophysics & Cosmology-- Cosmic Radiation
71 CLASSICAL AND QUANTUM MECHANICS
GENERAL PHYSICS
ANISOTROPY
CONVECTION
COSMIC RADIATION
DIFFUSION
DISTRIBUTION
ENERGY TRANSFER
HEAT TRANSFER
INTERPLANETARY MAGNETIC FIELDS
IONIZING RADIATIONS
MAGNETIC FIELDS
MASS TRANSFER
MATHEMATICAL MODELS
RADIATIONS
SOLAR RADIATION
STELLAR RADIATION
VARIATIONS