An Anisotropic Propagation Model for Galactic Cosmic Rays

Understand

Isotropic diffusion models for Galactic cosmic ray transport put tight constraints on the maximum convection velocity in the halo.

• For a half halo height of 4 kpc the maximum convection speed is limited to 40 km/s in the halo, since otherwise the constraints from local secondary to primary ratios and radioactive isotopes cannot be met.
• The ROSAT Galactic wind observations of wind speeds up to 760 km/s therefore constitute a problem for diffusion models.
• It is shown that such wind speeds are possible, if the diffusion coefficient in the halo is different from the diffusion coefficient in the disk.