Superbubbles, Galactic Dynamos and the Spike Instability
  We draw attention to a problem with the alpha-Omega dynamo when it is applied
to the origin of the galactic magnetic field under the assumption of perfect
flux freezing. The standard theory involves the expulsion of undesirable flux
and, because of flux freezing, the mass anchored on this flux also must be
expelled. The strong galactic gravitational field makes this impossible on
energetic grounds. It is shown that if only short pieces of the undesirable
field lines are expelled, then mass can flow down along these field lines
without requiring much energy. This expulsion of only short lines of force can
be accomplished by a spike instability associated with gigantic astrophysical
superbubbles. The physics of this instability is discussed and the results
enable an estimate to be made of the number of spikes in the galaxy. It appears
that there are probably enough spikes to cut all the undesirable lines into
pieces as short as a couple of kiloparsecs during a dynamo time of a billion
years. These cut pieces then may be randomly rotated in a dynamo time by
alpha-Omega diffusion and there is enough rotation to get rid of the
undesirable flux without expelling the fields themselves. The spike process
seems strong enough to allows the alpha-Omega dynamo to create the galactic
field without any trouble from the boundary condition problem.
