Simultaneous in situ and ground-based common-volume measurements for the investigation of the formation mechanism of Polar Mesosphere Winter Echoes

Relatively strong radar returns from mesospheric heights (~55–85 km) in the winter polar region result from coherent structures of electrons and are called Polar Mesosphere Winter Echoes (PMWE). The formation mechanism of this phenomenon is not understood. All relevant parameters potentially involved in the PMWE formation were measured in a common volume and subsequently analyzed. The combined results of rocket-borne and ground-based measurements of two rocket flights conclusively show that coherent structures are created by a turbulent process involving tiny charged meteor smoke particles.Radarrückstreusignale aus der Mesosphärenregion (~55-85 km) in polaren Breiten entstehen durch Reflexionen kohärenter Elektronenstrukturen und werden Polar Mesosphärische Winter Echos (PMWE) genannt. Erstmals wurden alle relevanten Parameter, die für den Entstehungsprozess von PMWE potentiell entscheidend sind in einem gemeinsamen Volumen mittels raketengetragenen in-situ Messungen und bodengebundenen Instrumenten untersucht. Diese Messungen geben ein einheitliches Bild: Turbulenz erzeugte in Verbindung mit geladenen Meteorstaubteilchen Strukturen, die mit dem Radar beobachtet wurden

Estimate of size distribution of charged MSPs measured in situ in winter during the WADIS-2 sounding rocket campaign

We present results of in situ measurements of mesosphere–lower thermosphere dusty-plasma densities including electrons, positive ions and charged aerosols conducted during the WADIS-2 sounding rocket campaign. The neutral air density was also measured, allowing for robust derivation of turbulence energy dissipation rates. A unique feature of these measurements is that they were done in a true common volume and with high spatial resolution. This allows for a reliable derivation of mean sizes and a size distribution function for the charged meteor smoke particles (MSPs). The mean particle radius derived from Schmidt numbers obtained from electron density fluctuations was ∼ 0.56 nm. We assumed a lognormal size distribution of the charged meteor smoke particles and derived the distribution width of 1.66 based on in situ-measured densities of different plasma constituents. We found that layers of enhanced meteor smoke particles' density measured by the particle detector coincide with enhanced Schmidt numbers obtained from the electron and neutral density fluctuations. Thus, we found that large particles with sizes  > 1 nm were stratified in layers of  ∼ 1 km thickness and lying some kilometers apart from each other

Simultaneous in Situ Measurements of Small-Scale Structures in Neutral, Plasma, and Atomic Oxygen Densities During the WADIS Sounding Rocket Project

In this paper we present an overview of measurements conducted during the WADIS-2 rocket campaign. We investigate the effect of small-scale processes like gravity waves and turbulence on the distribution of atomic oxygen and other species in the mesosphere–lower thermosphere (MLT) region. Our analysis suggests that density fluctuations of atomic oxygen are coupled to fluctuations of other constituents, i.e., plasma and neutrals. Our measurements show that all measured quantities, including winds, densities, and temperatures, reveal signatures of both waves and turbulence. We show observations of gravity wave saturation and breakdown together with simultaneous measurements of generated turbulence. Atomic oxygen inside turbulence layers shows two different spectral behaviors, which might imply a change in its diffusion properties

Sounding rocket project “PMWE” for investigation of polar mesosphere winter echoes

A first sounding rocket campaign dedicated to investigate the creation mechanism of Polar Mesosphere Winter Echoes (PMWE) was conducted in April 2018 from the north Norwegian Andøya Space Center (69 ∘ N, 16 ∘ E). Two instrumented sounding rockets were launched on 13th and 18th of April under PMWE and non-PMWE conditions, respectively. In this paper we give an overview of the PMWE sounding rocket mission. We describe and discuss some results of combined in situ and ground-based measurements which allow to verify existing PMWE theories. Our measurements ultimately show that: a) polar winter mesosphere is abounded with meteor smoke particles (MSP) and intermittent turbulent layers, b) all PMWE observed during this campaign can be explained by neutral air turbulence, c) turbulence creates small-scale structures in all D-region constituents, including free electrons; d) MSP ultimately influence the radar volume reflectivity by distorting the turbulence spectrum of electrons, e) the influence of MSP and of background electron density is just to increase SNR