  Recent diagnostic advances in gas-puff Z pinches at the Weizmann Institute
for the first time allow the reconstruction of the current flow as a function
of time and radius. These experiments show an unexpected radially-outward
motion of the current channel, as the plasma moves radially-inward [C.
Stollberg, Ph.D thesis, Weizmann Institute, 2019]. In this paper, a mechanism
that could explain this current evolution is described. We examine the impact
of advection on the distribution of current in a cylindrically symmetric
plasma. In the case of metric compression, with |v_r| proportional to r, the
current enclosed between each plasma fluid element and the axis is conserved,
and so the current profile maintains its shape. We show that for more general
velocity profiles, this simple behavior quickly breaks down, allowing for
non-conservation of current in a compressing conductor, rapid redistribution of
the current density, and even for the formation of reverse currents. In
particular, a specific inward radial velocity profile is shown to result in
radially-outward motion of the current channel, recovering the surprising
current evolution discovered at the Weizmann Institute.
