  In a simulation of SU(2) gauge theory we investigate, after maximal Abelian
projection, the dual Maxwell equations for colour field and monopole current
distributions around a static quark-antiquark pair Q_ Q in vacuo. Within the
dual superconductor picture we carry out a Ginzburg-Landau type analysis of the
flux tube profile. As a result we can determine the coherence length of the GL
wave function related to the monopole condensate, xi = .25(3) fm, to be
compared to the penetration length, lambda = >.15(2) fm (scaled with the string
tension).
