First observation of the overshoot effect for polar mesosphere winter echoes during radiowave electron temperature modulation

Abstract

Polar mesosphere winter echoes (PMWE), observed with the EISCAT VHF radar located near Tromsø, Norway on October 24, 2006, were modulated using the EISCAT Heating facility. The heater was turned on for 20 s and then off for 160 s. The experiment confirmed previous results that when the heater was switched on, the PMWE power dropped significantly compared to the undisturbed level measured before heating. The experiment showed for the first time that, after the heater was switched off, the PMWE strength overshot the value that it had before heating. By using data from 6 heating cycles we find that the overshoot effect is about 50% of the pre‐heating value, which is rather weak compared to 3–5 times for PMSE. No, or little recovery of PMWE strength during heating periods was observed. This may indicate the presence of very small dust particles, such as meteoric smoke particles.