On the source of plasma density and electric field perturbations in PMSE and PMWE regions

Polar mesospheric summer/winter echoes (PMSE/PMWE) are usually very strong radar echoes produced by ionospheric electron density fluctuations at half the radar wavelength. This paper studies the formation of electron density fluctuations in the PMSE/PMWE source region. Using a computational model, the current paper investigates the coupling of the neutral air turbulence with mesospheric dusty plasma as a generation source of fluctuations in plasma and dust densities as well as electric field. The impact of spectrum of irregularity wavelengths in neutral air turbulence including the presence of charged dust particles is investigated and extension of diffusion timescale for electron density fluctuations in smaller wavelength is studied. A comparison of the numerical results with VHF radar observations and in-situ rocket measurement of plasma density perturbations in the mesopause region is presented. The effect of dust density and dust-neutral collision frequencies on the coupling between neutral turbulence and the dust layer in PMSE source region is studied. The computational results are compared with the past theoretical predictions of impact of heavy charged dust on the wavenumber spectrum of electron irregularities. Formation of fluctuations in plasma and electric field in PMWE is then considered. The required plasma and dust parameters for neutral turbulence coupling in winter mesosphere are also determined.