PMSE long term observations using SuperDARN SANAE HF radar measurements

Abstract

It is known that the presence of nanometre-scale ice particles and neutral air turbulence in the Polar summer mesosphere modify the D-region plasma, resulting in strong backscatter. These strong backscatters are referred to as Polar Mesosphere Summer Echoes (PMSE). Although studies on PMSE have been ongoing for over three decades, aspects revealed by various instruments are still the subject of discussion. As a sequel to the paper by Ogunjobi et al. (2015), we report on the long term trends and variations in PMSE occurrence probability from Super Dual Auroral Radar Network (SuperDARN) high frequency (HF) radar measurements over the South African National Antarctic Expedition IV (SANAE IV). In this current paper, a simple multiple-filter technique is employed to obtain the occurrence probability rate for SuperDARN-PMSE during the summer periods for the years 1998 - 2007. The SuperDARN-PMSE occurrence probability rate in relation to geomagnetic activity is examined. The mesospheric neutral winds and temperature trends during these periods, are further studied and presented in this paper. Both the monthly and diurnal variations in occurrence are consistent with previous reports, confirming the presence of PMSE from SuperDARN SANAE IV radar measurements and the influence of pole to pole mesospheric transport circulation. The special mesospheric mean flow observed prior to the year 2002 is ascribed to the influence of solar activity. The SuperDARN-PMSE occurrence probability peaks with lowered geomagnetic activity. These present results support the hypothesis that the particle precipitation also plays an important role in SuperDARN-PMSE occurrence