Influence of external electromagnetic irradiation on formation and characteristics of a beam–plasma microwave discharge without external magnetic field: Polarization of the optical emission from such a discharge

For the first time in laboratory experiments, the influence of an external electromagnetic wave on beam–plasma discharge (BPD) characteristics was observed. The effect of irradiation of BPD by microwave signal was similar to the influence of microwave beam velocity modulation at the same frequencies and at the same parameters of electron beam and working gas pressure. This method could be explored in the field of study of large-scale aurora-type phenomena. Also included are materials from the first experimental studies of polarization of optical radiation from a beam–plasma system in the mode of beam–plasma microwave breakdown during the development of beam–plasma instability, accompanied by the influence of ponderomotive forces responsible for anisotropy in the velocity distribution of plasma electrons. Beam velocity modulation at frequency Fm close to plasma–electron frequency Fpe stabilized BPD and allowed the reliable measurements of the degree of polarization of some line of optical emission. For the first time, in experimental investigations of BPD without a magnetic field, the role of ponderomotive forces was noted, resulting in anisotropy of secondary electrons and polarization of discharge light emission. These studies confirm the significant role of the collective interaction of the electron beam with beam-generated plasma in explaining some radio-physical and optical phenomena in both artificial and natural auroral-type phenomena.