Microwave Propagation through a Plasma in a Magnetic Field

Experiments have been performed on the propagation of X-band ({}10¹⁰ cps) microwave signals through a plasma in a magnetic field ({}4 kG). The direction of propagation was parallel to the magnetic field lines. The regions of transmission and attenuation for both right-hand and left-hand circularly polarized microwave signals were located, at frequencies above and below both the electron cyclotron frequency and the electron plasma frequency. The range of densities covered was approximately 10¹⁰ electrons/cc to 10¹³ electrons/cc. Over part of this range the density measurements were made using an interferometer operating in both the right-hand and left-hand circularly polarized modes. Values of the refractive index greater than and less than unity were measured. Measurements were also made to determine the effect of electron temperature on the electron cyclotron cutoff frequency for the right-hand circularly polarized mode. A downward shift in the cutoff frequency was observed, which is in agreement with the theory.