Effects of drift on the transport of cosmic rays. VI - A three-dimensional model including diffusion

Abstract

We present the first results from a series of computer simulations of the solar modulation of galactic cosmic rays using a full three-dimensional model which incorporates all known important effects on particle transport, particle drifts, convection with the solar wind, energy loss, and anisotropic diffusion. The model is time-independent in the coordinate frame rotating with the Sun, so corotating effects can be studied. We consider modulation in an interplanetary magnetic field model in which the current sheet separating the northerm and southern solar hemispheres is warped and corotating with the Sun. The amplitude of the warp is varied to simulate possible solar cycle variation of the magnetic field. We find substantial effects due to the warp of the current sheet. Comparison of the model results with various data is presented. Among other things, we show that the intensity may decrease away from the current sheet for both signs of the magnetic field, as suggested by recent observations, and in contrast with inferences from earlier, more approximate calculations.