Radio spectral changes in the haloes of galaxies seen edge-on

Results of a Monte-Carlo study of the one-dimensional propagation of cosmic-ray electrons in the galactic photon field are presented. The effect of a galactic wind on the change of the radio spectral index with height above the galactic plane is investigated in particular. The dependence of this relation on various physical quantities is also investigated. A comparison of the model results with the spectral index-height relation on NGC 4631 and NGC 891 strongly suggest that these two galaxies have dynamic haloes.