On the heliolatitudinal variation of the galactic cosmic-ray intensity. Comparison with Ulysses measurements

G. Exarhos (1, 2) , X. Moussas (1)

1 Department of Astrophysics, Astronomy and Mechanics [Athens]
2 Siemens Hellas A.E.

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 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.

Domaines: Océan, Atmosphère; Sciences de la Terre

G. Exarhos, X. Moussas. On the heliolatitudinal variation of the galactic cosmic-ray intensity. Comparison with Ulysses measurements. Annales Geophysicae, 2003, 21 (6), pp.1341-1345. ⟨hal-00317094⟩