The Apparent Behavior of Electron Density during an Alternating O/X-Mode Heating Experiment

We present the observations of artificial ionospheric modification experiment EISCAT on 18 October 2012 in Tromsø, Norway. When pump alternating O mode and X is switched on, UHF radar observation shows some strong enhancements electron density, ion lines plasma lines. Based existing theories, we find following: First, during experiment, frequency line (fL), (fia) (fh) matches fL = fh − 3fia 5fia occasionally demonstrated that cascade process occurred. Second, through quantitative calculation, found O-mode component mixed X-mode wave satisfies thresholds parametric decay instability oscillation two-stream instability, from which infer HF-induced (HFPLs) HF-enhanced (HFILs) observed pulse could have been caused by wave. Third, apparent over a wide altitude range (from approximately reflection to ~670 km) density pulse, also does not, fact, correspond true increase but due enhancement or backscatter induced unknown mechanism.