Session 2: Solar, Planetary and Space Physics

Title: The heliolatitudinal variation of the galactic cosmic-ray intensity with a shell model. Comparison with Ulysses measurements
Author(s): G. Exarhos, X. Moussas (Poster)
Contact: X. Moussas, National University of Athens,

  We study the dependence of cosmic rays with heliolatitude using a simple  method and compare the results with the actual data from Ulysses and IMP spacecraft. We reproduce the galactic cosmic-ray heliographic latitudinal intensity variations applying a semi-empirical 2-D diffusion-convection model for the cosmic ray transport in the interplanetary space. This model is a modification of our previous 1-D model (Exarhos and Moussas, 2001) and includes not only the radial diffusion of the cosmic-ray particles but also the latitudinal diffusion. Dividing the interplanetary region into "spherical magnetic sectors" (a small heliolatitudinal extension of a spherical magnetized solar wind plasma shell) that travel into the interplanetary space at the solar wind velocity, we calculate the cosmic-ray intensity for different heliographic latitudes as a series of successive intensity drops that all these "spherical magnetic sectors", between the Sun and the heliospheric termination shock, cause to the unmodulated galactic cosmic-ray intensity. Our results are compared with the Ulysses cosmic-ray measurements obtained during the first pole-to-pole passage from mid-1994 to mid-1995.