MAGNETIC BUOYANCY AND THE GALACTIC DYNAMO

Concentrating on the role of the Parker instability, we consider an in trinsic instability of the magnetic field as a possible origin of the alpha-effect taking part in the dynamo action. We examine the possibil ity that the magnetic field is concentrated in braked, isolated flux t ubes extended between molecular clouds. We estimate that the ionized g as moving along the tube of the total length 100pc, the mean interclou d distance, acquires due to Coriolis force the cyclonic velocity congr uent-to 1.5kms-1. The balance of the drag force and the buoyancy force acting on the rising flux tubes establishes the characteristic veloci ty of rise congruent-to 1kms-1. We point out that these slow flux tube velocities, can lead to the comparatively small diffusivity coefficie nt eta(T) congruent-to 0.06 . 10(26)cm2s-1. The estimation of helicity in this model gives alpha congruent-to 0.6kms-1. This result leads to the conclusion that the dynamo number D = R(alpha)R(omega) can be inc reased even by a factor of 100 with respect to the standard model.