A model, based on ion transport along the plasma in vacuum arcs, is proposed to explain the evolution of charge states. Physical arguments implementing such a model are given, and the charge state fluxes are evaluated. The systematic trends of the particle current fractions are seen to be alike for the theoretical and experimental values, and good quantitative agreement is found for electron temperatures, higher than the generally accepted values. Comments regarding the future work and the effect of a magnetic field are stated. (C) 1997 American Institute of Physics.