HF-induced airglow at magnetic zenith: theoretical considerations

Abstract. Observations of airglow at 630nm (red line) and 557.7nm (green line) during HF modification experiments at the High Frequency Active Auroral Research Program (HAARP) heating facility are analyzed. We propose a theoretical framework for understanding the generation of Langmuir and ion acoustic waves during magnetic zenith injections. We show that observations of HF-induced airglow in an underdense ionosphere as well as a decrease in the height of the emitting volume are consistent with this scenario.