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Ann. Geophys., 21, 1341-1345, 2003
www.ann-geophys.net/21/1341/2003/
© European Geosciences Union 2003
On the heliolatitudinal variation of the galactic cosmic-ray intensity. Comparison with Ulysses measurements
G. Exarhos1,2 and X. Moussas1
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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