GALACTIC HALO MAGNETIC-FIELDS DUE TO A SPIKY WIND

To approach the galactic dynamo we solve the mean-field induction equa tion (with a 2D time-stepping code after Elstner et al. 1990) for a we ll-defined flow system. The turbulence pattern is assumed to be distri buted in vertical direction (but to be uniform along the radius). It a lso extends to the galactic halo, where a fixed value of the rms veloc ity is defined. The mid-plane turbulence intensity is the free paramet er in the theory. The turbulence electromotive force is computed witho ut inclusion of the density stratification. The mean flow consists of the global galactic rotation and a vertical wind. The wind is increasi ng with the disk height. Uniform as well as spike-like radial profiles of the wind intensity are used. The dynamo is suppressed if intensive uniform winds are acting in the dynamo-active region. For winds separ ated from the dynamo domain there is generally a rather weak influence of the wind on the resulting field strength. The field geometry, howe ver is drastically changed in the wind region. Weak vertical field com ponents occur for horizontally uniform winds while rather strong verti cal magnetic fields belong to a highly nonuniform ('spiky') wind profi le.