SOME SEASONAL HEMISPHERIC SIMILARITIES IN F(0)F2 QUASI-2-DAY OSCILLATIONS

The annual variations of the amplitude, period, and probability of exi stence of f(0)F2 quasi-2-day oscillations at middle latitudes in both northern and southern hemispheres are investigated. The f(0)F2 hourly data for the period 1977-1982 for stations Kiev (50.5 degrees N, 30.5 degrees E) and Wakkanai (45.39 degrees N, 141.69 degrees E) for the no rthern hemisphere and Kerguelen (49.35 degrees S, 70.24 degrees E) and Campbell Island (52.6 degrees S, 169.1 degrees E) for the southern he misphere are used for analysis. It is found that there is a strong ten dency for hemispheric similarities in the seasonal variations of oscil lation amplitude, period, and probability of existence. The annual var iations of tile oscillation amplitude are modulated by the 12-month he mispheric and semiannual geomagnetic waves; the dominant period of osc illation is maximum in summer (50-51 hours) and minimum in winter (47- 49 hours), and the probability of existence has a maximum in the summe r half year and minimum in the winter half year. The seasonal similari ties in the annual variations of the oscillation period and the probab ility of existence show the possible influence of the planetary 2-day wave in the middle neutral atmosphere on the electron density variatio ns in the F region.