  A new cosmic string model specified by two independent mass parameters is
introduced for the purpose of providing a realistic representation of the
macroscopic dynamical behaviour of Witten type (superconducting) vortex defects
of the vacuum. Unlike the self dual single mass parameter models previously
used for this purpose, the new model successfully represents the effect of
current saturation and the feature that wiggle propagation remains supersonic
even in the weak current limit.
