  One of the unsolved problems in cosmic ray (CR) physics is the small radial
gradient of the gamma-ray intensity compared to the inferred CR source
distribution in the Galactic disk. In diffusive CR propagation models the most
natural explanation is very efficient spatial mixing due to MHD turbulence in
the interstellar medium. However, even in the most favorable case of a very
large diffusive CR halo the gamma-ray gradient is still larger than observed.
In our view such a small gradient could be the result of strong advection by a
Galactic wind. We show that a small gamma-ray gradient can be obtained, if the
diffusion region does NOT extend far above the Galactic plane. Important
ingredients of our model are: (i) anisotropic CR diffusion, (ii) strong radial
and vertical gradients of the advection velocity (due to faster winds above
higher CR source density regions).
