  In theories with flat directions containing vortices, such as supersymmetric
QED, there is a vacuum selection effect in the allowed asymptotic
configurations. We explain the role played by gauge fields in this effect and
give a simple criterion for determining what vacua will be chosen, namely those
that minimise the vector mass. We then consider the effect of vacuum selection
on stable (BPS) non-topological vortices in a simple Abelian model with N=2
supersymmetry which occurs as a low energy limit of Calabi-Yau
compactifications of type II superstrings. In this case the magnetic flux
spreads over an arbitrarily large area. We discuss the implications for
cosmology and for superstring inspired magnetic confinement scenarios.
