A statistical study of the polar mesosphere summer echoes overshoot effect with EISCAT VHF during the present solar cycle

We have conducted observational campaigns using EISCAT radars and the heater to modify the strength of the polar mesosphere summer echoes (PMSE). In 2003, Havnes et al. predicted and measured a PMSE overshoot effect. The overshoot effect was strong and frequently observed in the next years following its discovery, but afterwards it has become weaker and rarely observed. However, it seems that this effect has reappeared in our most recent summer campaign in 2013. We will show a statistical study of the occurrence and strength of the heating and the overshoot effect based on observations around the PMSE peak season in the years 2003-2013, this corresponds to approximately a solar cycle. It is know that a major factor controlling the electron heating at the PMSE layer is the electron density below it. It is plausible that the electron density has been unfavorable in the case when the PMSE overshoot was absent. The aim of this study is to verify if the occurrence of the PMSE overshoot and heating effects are correlated with changes in the electron density as determined by the phase of the solar cycle. However, we cannot exclude that other factors are at play.