Abstract
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.
Highlights
It is well known that injections of high-power, highfrequency (HF) radio waves strongly perturb ionospheric plasmas
Stochastic interactions heat the bulk of electrons (e.g. Gurevich et al, 1985; Dimant et al, 1992; Mantas and Carlson, 1996; Gurevich and Milikh, 1997; Istomin and Leyser, 2003)
Depending on the energy density of the uh-turbulence, which depends on the ERP, the induced scattering process may deliver the Langmuir wave energy Wl to the region kl→0 (Langmuir condensate) (Zakharov et al, 1976)
Summary
It is well known that injections of high-power, highfrequency (HF) radio waves strongly perturb ionospheric plasmas. Gustavsson et al (2002) emphasized that ςgr >0.1 requires unrealizable electron temperatures Te>2 eV, pointing out the importance of electron acceleration in the highenergy tail The latter stems from resonant interactions with plasma turbulence generated by heater waves. Kosch et al (2002b) showed that the intensity of red-line emissions decreased when the heating frequency approached an electron gyro-harmonic, pointing out the importance of upper hybrid turbulence at MZ. Mishin et al (2004) suggested a scenario for exciting plasma turbulence with subsequent electron heating and acceleration in the HF-illuminated region at MZ This scenario, depicted, explores the results of Kuo et al (1997), who showed that the OTSI can be excited by upper hybrid
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