MAGNETIC DIFFUSION DUE TO SUPERNOVA EXPLOSIONS AND SUPERBUBBLES IN THE GALACTIC DISK

We derive a general analytical expression for the turbulent magnetic diffusivity tensor due to an ensemble of explosions. We then particularize to the case when explosions arise from supernovae and superbubbles in the Galactic disk. We find that superbubbles dominate the production of magnetic diffusion, especially high above the midplane. This happens both because interactions with superbubbles are more frequent and because superbubbles are able to carry field lines farther than isolated supernovae. Since most explosions take place at low altitude, the total vertical diffusivity (due to supernovae and superbubbles together) is small at the midplane (approximately 6 x 10(24) cm2 s-1 at the solar circle); it increases rapidly with height up to approximately 300 pc and remains roughly uniform (approximately 5 x 10(25) cm2 s-1 at R.) between 300 and 800 pc. The total horizontal diffusivity is maximum at the midplane (approximately 2.7 x 10(25) cm2 s-1 at R.) and falls off slowly with height.