QUASI 2-DAY OSCILLATION OF THE IONOSPHERE DURING SUMMER 1992

The relationship between quasi 2-day (QTD) oscillations in the neutral wind near 90 km altitude, and in the critical plasma frequency (f(o)F (2)) of the ionospheric F region, is investigated for the June-Septemb er 1992 period. Wind data are analyzed from MF radar stations at Chris tmas Island (1.9 degrees N, 202.7 degrees E), Hawaii (20.8 degrees N, 203.5 degrees E), and Saskatoon (52.1 degrees N, 253.4 degrees E) with emphasis ori characterizing temporal evolutions of the amplitude and period of the QTD oscillation; four identifiable ''events'' are found, one each in the months of June, July, August, and September. Evidence for corresponding +/-0.5-1.0 MHz QTD oscillations in f(o)F(2) is foun d in data from about half of the 24 ionosonde stations examined. Ident ification of such concurrent occurrences is complicated by the lack of consistency between QTD ''burst'' characteristics between station loc ations (for both wind and f(o)F(2)) and between the meridional and zon al components of the QTD wind variations. These differences are probab ly due to the sensitivity of the QTD wind oscillation to the backgroun d wind structure, which contains latitude and longitude dependences. E vidence is presented for a zonal wavenumber one (s = 1) longitude depe ndence for the middle-latitude f(o)F(2) oscillation, which contradicts the expected s = 3 dependence of the mesosphere/lower thermosphere (M LT) neutral winds, but which is consistent with the ''first type'' of QTD oscillation in f(o)F(2) at middle latitudes described by Apostolov et al. [1995]. The data presented here are not able to shed light on which of several potential mechanisms lead to the QTD oscillation in f (o)F(2).