Neutral air turbulence in the mesosphere and associated polar mesospheric summer echoes (PMSEs)

Abstract. This paper presents the first simultaneous four radar frequency observations of the PMSE region under varying neutral air turbulence conditions. Radar frequencies of 8, 56, 224, and 930 MHz are used in this study. Three days of experimental observations associated with EISCAT are presented. Numerical simulations of mesospheric dusty/ice plasma associated with the observed radar frequencies are presented. The effect of neutral air turbulence on the generation and strength of plasma density perturbations associated with PMSE using four radar frequencies and in the presence of various dust parameters is investigated. Using the model it is shown that the well-known neutral air turbulence in presence of heavy dust particles, so-called fossil turbulence, can largely explain the observed radar cross-section at four radar frequencies. The effect of initial turbulence amplitude along with dust charging and diffusion in the presence of various dust parameters is investigated using the computational model. Specifically, the response of diffusion to charging time scales, plasma density fluctuation amplitude to the background dusty plasma parameters are discussed. Several key parameters in dusty plasma responsible for the PMSE observations are determined.