Helicity fluctuation, generation of linking number and effect on   resistivity
  The energy of the stochastic magnetic field is bounded from below by a topological quantity expressing the degree of linkage of the field lines. When the bound is saturated one can assume that the storage of a certain magnetic energy requires a minimal degree of topological complexity. It is then possible to infer a connection between the helicity content and the average curvature of the magnetic field lines. The random curvature induce random drifts leading to an additional dissipation and modified resistivity. 
F. Spineanu and M. Vlad