Tristan Staszak (2021) Simultaneous in situ and ground-based common-volume measurements for the investigation of the formation mechanism of Polar Mesosphere Winter Echoes (PhD Thesis)

Relatively strong radar returns from mesospheric heights ( ~55-85 km) in the winter polar region have been detected by radar since the late 1970s. These observations result from coherent structures of electrons and are called Polar Mesosphere Winter Echoes (PMWE). Since the annual season of PMWE observations is relatively long, and PMWE detections cover an extensive altitude range, these echoes have an enormous potential for utilization as a tracer for geophysical processes. However, 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 for the first time. 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 MSPs. By analyzing the background winds, it could be shown that the turbulent structures are most likely created by a braking gravity wave. Another result of this thesis is that the intensity of turbulence varies by approximately one order of magnitude within only a few buoyancy periods (i.e., minutes) and thereby essentially influences whether PMWE is formed or not.