We present an analytical model for the hydrodynamic outflow from the disk of a starburst galaxy .
The model is used to calculate the cosmic ray propagation and the radio intensity distribution in the nuclear starbust region of NGC 253 .
We find that the cosmic ray energy production rate of the central 600 pc of NGC 253 is about 3 \cdot 10 ^ { 41 } erg s ^ { -1 } , that is about 15 percent of the total mechanical supernova power .
For this inner region we estimate a terminal outflow velocity of 900 km s ^ { -1 } and a mass loss rate of \dot { M } = 2 \div 4 M _ { \odot } per year .