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

• Published in: Universe (Basel) 2021-12, Vol.7 (8), p.274
• Main Authors: Li, Zeyun, Li, Qingfeng, Fang, Hanxian, Gong, Hongwei
• Format: Article
• Language: English
• Subjects: Altitude; electron density; Electrons; Experiments; ion line; Ionosphere; ionospheric modification; Magnetic fields; Plasma; plasma line; Power; Radar; Software
• ISSN: 2218-1997; 2218-1997
• DOI: 10.3390/universe7080274

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