A characterization of plasma fluctuations within a hall discharge

Experimental results are presented for studies of low (2-20 kHz) and interm ediate-frequency (20-100 kHz) oscillations in crossed-field closed electron -drift Hall discharges. Conditional sampling using two electrostatic probes is used to identify and extract properties of coherent structures associat ed with the propagation of azimuthal and longitudinal instabilities within the discharge channel. The azimuthal component phase velocities are determi ned for a wide range of wave frequencies and over characteristic regimes of operation of these devices. A variety of propagation modes are observed an d analyzed, including the appearance of an induced mode due to the presence of the probes themselves. This later result is believed to be the first di rect evidence of how fluctuations can be influenced in these Hall discharge s using relatively simple actuation methods.