Galactic cosmic-ray sidereal anisotropies and the heliosphere

By analyzing the sidereal daily variations recorded in 44 underground muon telescopes in two hemispheres, Hall et al. (1999) devised an empirical model of the cosmic-ray anisotropy. To investigate the influence of the large-scale structure on high-energy cosmic-ray propagation, we calculate cosmic-ray orbits in the model heliosphere obtained by Washimi and Tanaka (1996) from the MHD simulations of the heliosphere. By calculating the energy gain and loss of particles due to the electric field induced in the magnetized plasma flow, we present a model anisotropy of 10000 GeV particles traveling on nearly radial paths to the earth. The model shows an acceleration region existing in the apex (α : 260o 20o) direction, due to the significant electric field induced on the apex sides of the solar wind termination shock. These results are discussed in relation with the anisotropy reported from the observations.