EXPERIMENTAL INVESTIGATION OF ION-ACOUSTIC DOUBLE-LAYERS IN THE ELECTRON FLOW ACROSS MULTIDIPOLE MAGNETIC-FIELDS

In this experiment, a cold electron flow is produced across the multidipole field of a magnetic fence. For electron flow velocities above the ion-acoustic speed (v(d) > C(s)), generation of ion-acoustic instability is observed beyond the magnetic sheath region of the fence. The anomalous resistivity associated with the turbulence is large enough to give rise to a plasma potential jump over a long distance (L >> lambda-D), known as a double-layer. The anomalous particle transport process leading to the formation of the small-amplitude double-layer is related to a bootstrap mechanism.