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Alpha-tensor and diffusivity tensor due to supernovae and superbubbles in the Galactic disk
Received 17 December 1997 / Accepted 16 March 1998
Dynamo action (i.e., magnetic field amplification at large scales) requires the presence of turbulent motions, whose effects are traditionally described by the alpha- and diffusivity tensors. In the present paper, we compute the various components of these tensors, also known as the dynamo parameters, as a function of Galactic radius and height, on the hypothesis that the turbulent motions responsible for dynamo action in our Galaxy arise from supernova explosions. To that end, we combine ingredients taken from several earlier studies, including an up-to-date model of the interstellar medium, a numerical code designed to follow the expansion of supernova remnants and superbubbles in this model ISM, and analytical formulae for the dynamo parameters. Our computed dynamo parameters turn out to be predominantly due to clustered supernovae. They peak at about 7 kpc from the rotation axis and kpc from the midplane, reaching values in the expected range for magnetic field amplification.
Key words: Galaxy: general ISM: bubbles; magnetic fields; supernova remnants
Send offprint requests to: Katia Ferrière
Online publication: June 18, 1998