Three dimensional model of the interplanetary magnetic field and 27-day variation of the galactic cosmic ray intensity

Abstract

We present a model of the 27-day variation of the galactic cosmic ray (GCR) intensity for three dimensional (3-D) heliosphere with the heliolongitudinal and heliolatitudinal dependent radial solar wind speed for the period of 1995 – minimum epoch of solar activity (A > 0). In the present model we implement heliolongitudinal asymmetry of solar wind velocity reproducing as the sum of first and second harmonics depending on the heliolatitudes and the regular part of the solar wind velocity (V0) changing versus heliolatitudes in accord to in situ measurements of the Ulysses spacecraft. We show that the range of changes of the sum of the first and second harmonics of the 27-day variation of the GCR intensity for Kiel neutron monitor is little less than expected from the modelling, however, they are comparable. © 2011 Author(s).