Extraction of polar mesosphere summer echoes from SuperDARN data

An algorithm for automated extraction of polar mesosphere summer echoes (PMSE) from near-range measurements of the Super Dual Auroral Radar Network (SuperDARN) is applied to observations obtained by the Syowa East (69.01°S, 38.61°E) and Iceland East (63.77°N, -20.54°W) radars whose fields-of-view are magnetically conjugate. The rate of PMSE occurrence in the SuperDARN data is greatly enhanced in summer months, reaching a maximum of ≈90% in Iceland and 60% in Syowa near the summer solstice. The diurnal variation of PMSE occurrence reaches a maximum near the noon meridian, with a distinct minimum at 20LT. These features are consistent with those derived from previous VHF radar observations, suggesting that the SuperDARN data contain large numbers of PMSE events. The interhemispheric asymmetry of PMSE occurrence is also estimated, and it is shown that the PMSE activity is ≈1.5 times higher in the Northern Hemisphere (N.H.) than in the Southern Hemisphere (S.H.). Thus, interhemispheric asymmetry in PMSE occurrence appears to exist, but is much weaker than that predicted previously based on VHF radar observations.