Enhancement of stimulated electromagnetic emission during two frequency ionospheric heating experiments

Abstract

We have discovered that stimulated electromagnetic emission (SEE), excited by a powerful electromagnetic (EM) wave (pump 1) in the ionosphere, can be enhanced by a second high power EM wave (pump 2) with a higher frequency. For frequency separations near 0.4 MHz, the downshifted SEE in a 40 kHz band below the frequency of pump 1 is increased by 2 dB when pump 2 is turned on. We theorize that a second EM wave generates plasma irregularities that facilitate the mode conversion of electrostatic waves to yield enhanced EM emissions from pump 1.