  We study the stability of superconducting strings in a U(1)_{local} x
U(1)_{global} model coupled via a gauge field interaction term to U(1)
Abelian-Higgs strings. The effect of the interaction on current stability is
numerically investigated by varying the relevant parameters within the physical
limits of our model. We find that the propagation speed of transverse (resp.
longitudinal) perturbations increases (decreases) with increasing binding
between the superconducting and Abelian-Higgs string. Moreover, we observe that
for small enough width of the flux tube of the superconducting string and/or
large enough interaction between the superconducting and the Abelian-Higgs
string superconducting strings cannot carry space-like, i.e. magnetic currents.
Our model can be seen as a field theoretical realization of bound states of p
F-strings and q superconducting D-strings and has important implications to
vorton formation during the evolution of networks of such strings.
