  The possibility of the magnetic flux expulsion from the Galaxy in the
superbubble (SB) explosions, important for the Alpha-Omega dynamo, is
considered. Special emphasis is put on the investigation of the downsliding of
the matter from the top of the shell formed by the SB explosion which is able
to influence the kinematics of the shell. It is shown that either Galactic
gravity or the development of the Rayleigh-Taylor instabilities in the shell
limit the SB expansion, thus, making impossible magnetic flux expulsion. The
effect of the cosmic rays in the shell on the sliding is considered and it is
shown that it is negligible compared to Galactic gravity. Thus, the question of
possible mechanism of flux expulsion in the Alpha-Omega dynamo remains open.
