Introduction

In the theory of cosmic ray modulation in the heliosphere, i.e. the region around the sun that is dominated by the solar wind plasma (which itself represents the expanding outer part of the sun's atmosphere), there occurs the following hydrodynamical version of a cosmic ray (CR) transport- or energy equation: $$ \nabla\cdot(\stackrel{\leftrightarrow}{\kappa} \nabla p) +(-\vec{v}_{sw} - \gamma \vec{v}_{dr})\cdot\nabla p +[-\gamma (\nabla\cdot \vec{v}_{sw})] p=0 $$ The quantities in this equation are:

$p (\vec{r})$	=	pressure or energy density of the cosmic rays
$\vec{v}_{sw}$	=	velocity of the solar wind
$\vec{v}_{dr}$	=	drift velocity of the cosmic rays
$\gamma$	=	constant polytropic index of the cosmic ray gas
$\stackrel{\leftrightarrow}{\kappa} $	=	the diffusion tensor

The above equation describes the diffusion and drift of the cosmic ray particles in the interplanetary magnetic field and their convection and adiabatic deceleration due to the expanding solar wind plasma. The pressure indicates the cosmic ray intensity at a position $\vec{r}$. More about the physics of CR is found in astronomical literature [ HF ] , [ GR ] .