Reg Edwards wrote:
The non-uniform current does not arise from radiation but from the
distributed capacitance of the wire turns on the helix to its
surroundings.

How about the fact that it is a *standing wave antenna* with a
forward traveling wave in one direction and a reverse traveling
wave in the other direction? The net current is the sum of
those two current components and their phasors are rotating
in opposite directions.
--
73, Cecil http://www.qsl.net/w5dxp