  The low-frequency instability of a magnetized plasma column and the anomalous
radial plasma convection are shown to be linked with the existence of a radial
cross-field current along a plasma channel rotating around the central
magnetized plasma. The direct observation of the rotating plasma is obtained
using an ultra-fast intensified camera. The ionizing electrons injected along
the axis of the plasma column contribute to the accumulation of negative
charges when the axial collector is at floating potential. The required
neutrality leads to the continuous radial expulsion of energetic electrons and
to the formation of a rotating plasma channel (m=1 unstable wave). This
situation has previously been interpreted erroneously as a diamagnetic drift
wave.
