Emission, absorption, and tunneling of whistler waves in an inhomogeneous magnetic field

Measurements of electron cyclotron emission parallel to a magnetic field in the regime where finite density effects are important and measurements of electron cyclotron wave tunneling parallel to a magnetic field are reported. The experiments were conducted in a low-temperature (T/sub e/ approx.2 eV) moderate-density (n/sub e/ = 3 x 109--3 x 1012 cm-3) gas discharge plasma in a magnetic mirror geometry. Experimental results are compared with two models, both of which employ Kirchoff's law to relate emission and absorption. In one model, absorption from hot-plasma theory is calculated and in the other a cold-plasma Budden tunneling type analysis is employed. Both models are in reasonable agreement, with the data generally bracketing the experimental results, and the experiment could not resolve which model is superior. The utility of whistler mode cyclotron emission as an electron temperature diagnostic measurement on mirror machines is confirmed