Electron–ion temperature ratio estimations in the summer polar mesosphere when subject to HF radio wave heating

• We inferred mesospheric Te/Ti during artificial HF heating.
• Te/Ti model results match estimates from our novel method.
• The method uses ISR data and the radar equation dependence on Te/Ti.
• PMSE weakening is consistent with Te enhancements of approx. 10 times.
• Independent validation of mesospheric Te/Ti is done by ISR data at higher altitudes.

We have inferred the electron temperature enhancements above mesospheric altitudes under Polar Mesospheric Summer Echoes (PMSE) conditions when the ionosphere is exposed to artificial HF radio wave heating. The proposed method uses the dependence of the radar cross section on the electron-to-ion temperature ratio to infer the heating factor from incoherent scatter radar (ISR) power measurements above 90 km. Model heating temperatures match our ISR estimations between 90 and 130 km with 0.94 Pearson correlation index. The PMSE strength measured by the MORRO MST radar is about 50% weaker during the heater-on period when the modeled electron-to-ion mesospheric temperature is approximately 10 times greater than the unperturbed value. No PMSE weakening is found when the mesospheric temperature enhancement is by a factor of three or less. The PMSE weakening and its absence are consistent with the modeled mesospheric electron temperatures. This consistency supports to the proposed method for estimating mesospheric electron temperatures achieved by independent MST and ISR radar measurements.