THE FULL ALPHA-TENSOR DUE TO SUPERNOVA EXPLOSIONS AND SUPERBUBBLES IN THE GALACTIC DISK

In this paper we investigate the impact of turbulent motions on the mean magnetic field in our Galaxy. We calculate the alpha-tensor which linearly relates the electromotive force due to turbulent motions to the mean magnetic field. We first derive a general analytical expression for this tensor when turbulence is driven by an ensemble of axisymmetric explosions. We then apply our general results to supernova explosions and to superbubbles. We find that superbubbles are more efficient than isolated supernovae at removing magnetic flux from the Galactic disk, by a factor approximately 2 near the midplane, and at generating magnetic field in the direction perpendicular to the prevailing field (alpha-effect) by a factor approximately 6 near the midplane. In the solar neighborhood, the total magnetic escape velocity increases from zero at the midplane to a maximum value of 1.8 km s-1 at an altitude of 150 pc, while the parameter associated with the azimuthal (radial) alpha-effect increases (decreases) from zero at the midplane to 0.18 km s-1 (-0.025 km s-1) at an altitude of 250 pc.