First observations of the artificial modulation of polar mesospheric winter echoes

Abstract

We demonstrate for the first time that the application of ionospheric heating can affect the strength of polar mesospheric winter echoes (PMWE) detected by VHF radar. PMWE were observed between 61.8 and 68.5 km altitude and we show that the signal strength can be modulated with 10‐second and 1‐minute cycles. The structures that cause PMWE are shown to extend over several hundred meters (∼300 m) with echoes existing in two height regimes simultaneously and a descent in altitude indicative of gravity wave effects. The effect on PMWE of ionospheric heating has similar gross features to those for PMSE: a sharp decrease in power when HF heating is switched on followed by a sharp increase when heating is switched off. During the period of active heating there is some recovery in echo power suggestive of dust control of the PMWE.