STIMULATED ELECTROMAGNETIC EMISSIONS FROM MAGNETIZED AND INHOMOGENEOUS-PLASMA

We model the radio emission spectrum for an electromagnetically pumped, magnetized and inhomogeneous plasma and compare the results to observations of upper sideband features of stimulated electromagnetic emissions (SEE) in ionospheric heating experiments when the heater frequency, omega-0, is near harmonics of the ionospheric electron cyclotron frequency, OMEGA-e. Our model involves solving the equations of motion for electrons in an external electromagnetic pump wave and geomagnetic field to calculate, for an inhomogeneous plasma, a current which excites electron Bernstein and lower hybrid waves. We reinsert this current into the equations of motion and continue in an iterative manner. The result is a current which depends on density gradients across the geomagnetic field. The current intensifies with decreasing density gradient scale. It has a frequency omega = 2-omega-0 - p-OMEGA-e, where p is an integer, is resonant for omega-0 almost-equal-to p-OMEGA-e and for which there is a cutoff in the spectra at about 10 kHz above the pump frequency. Our results agree with observations made in SEE experiments.