Dependence of Altitudes of HFPL and HFIL on Electron Temperature during Ionospheric Heating

This paper focuses on the altitude characteristics of the high frequency pump enhanced ion line (HFIL) and plasma line (HFPL) during an ionospheric heating campaign with a pump frequency near the fifth gyro-harmonic at the EISCAT. Those UHF observations show that the observing altitude of the HFIL and HFPL varies as a function of pump frequency. In conclusion, the altitude variations of the HFIL and HFPL are essentially due to the thermal effect induced by the ionospheric heating.