Transmission characteristics of cyclotron harmonic waves in plasma

In recent years the importance of cyclotron harmonic waves has become apparent in many branches of plasma physics. For example, it has been demonstrated that they are involved in the anomalously high noise radiation near the electron cyclotron harmonic frequencies that has been observed from thermonuclear fusion study devices, and that they can explain the cyclotron harmonic resonances observed in satellite studies of the ionosphere. In this paper experiments on propagation perpendicular to a magnetic field in a low-pressure mercury-vapour discharge are described. This mode is particularly important since it is not subject to Landau damping. The relevant dispersion curves are compared with results of the experimental study, and show evidence of such transmission across the plasma, between two parallel cylindrical probes. Cyclotron resonance phenomena have many potential applications to plasma diagnostics, the theory of extra-terrestrial noise excitation and to microwave oscillators and amplifiers. Some of these are discussed briefly.