Goertz and Morfill (1983) propose that spokes on Saturn's rings form under
radially moving plasma clouds produced by meteoroid impacts. We demonstrate
that the speed at which a plasma cloud can move relative to the ring material
is bounded from above by the difference between the Keplerian and corotation
velocities. The radial orientation of new spokes requires radial speeds that
are at least an order of magnitude larger than this upper limit, thus the model
advanced by Goertz and Morfill fails to make radial spokes.Comment: 15 pages, 2 figures, Icarus in pres