Articles | Volume 21, issue 6
Ann. Geophys., 21, 1341–1345, 2003

Special issue: Ulysses and Beyond

Ann. Geophys., 21, 1341–1345, 2003

  30 Jun 2003

30 Jun 2003

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

G. Exarhos2,1 and X. Moussas1 G. Exarhos and X. Moussas
  • 1Laboratory of Astrophysics, Department of Astrophysics, Astronomy and Mechanics, School of Science, Faculty of Physics, National and Kapodistrian University of Athens, Panepistimiopolis GR 15783, Zografos, Athens, Greece
  • 2Siemens Hellas A.E., Promitheos 12, Nea Kifisia, Athens, Greece

Abstract. 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.

Key words. Interplanetary physics (cosmic rays; interplanetray magnetic fields; solar wind plasma)

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