Velocity skin effect with plasma armature

The velocity skin effect is analyzed for a plasma armature railgun system. The effect is shown to produce a nearly uniform current density distribution. The governing equation is derived and solved numerically for the case in which plasma armature parameters vary only in the axial direction. This result is used to compute the temporal signature to be expected of axial B probes. Comparison with experimental data indicates that some mechanism other than the velocity skin effect is responsible for determining the current density distribution in a plasma armature. It is concluded that a likely process for explaining the observed results is the transport of magnetic flux by plasma flow, the flow being induced by viscous drag occurring at the rail/insulator surfaces