EFFECT OF THE EXPLOSION OF SUPERNOVAE AND SUPERBUBBLES ON THE GALACTIC DYNAMO

We derive a simple analytical expression for the alpha-parameter, based on the action of supernova and superbubble explosions on the mean Galactic magnetic field. We find that superbubbles are about 7 times more efficient than isolated supernovae at generating radial field from azimuthal field (alpha-effect). The resulting alpha-parameter increases linearly with Galactic height up to approximately 100 pc (where it reaches a value of order 0.13 km s-1), then flattens out and turns over at approximately 250 pc.