Low-Frequency Electrostatic Waves in a Weakly Ionized Plasma under a Weak Magnetic Field

Abstract

Investigation has been made of propagating waves excited by a small coil surrounding a plasma column produced by a dc discharge at a pressure of a few μHg under a weak axial magnetic field. Measurements are made mainly of the (0, 2) mode excited on the cathode side of the exciting coil in the frequency range of 17–60 kc/sec. The waves are observed to have a forward-wave dispersion for lower frequencies, but a backward-wave dispersion for higher frequencies in this range. Their phase velocities are directed toward the exciter. These waves are theoretically predicted to propagate in a weakly ionized, current-carrying, uniform plasma under a weak magnetic field. The experimental data are in reasonable agreement with the theoretical results. The (0, 1) and (1, 1) modes excited on the cathode and anode sides are also studied experimentally in some detail. Some of the data are not interpreted yet.