Evidence of quasi-biennial wind oscillation in the mid-latitude lower thermosphere, obtained from ionospheric drift measurements in the LF range

Abstract

From ionospheric drift measurements in the low-frequency range, carried out continuously for many years on three different measuring paths at the observatories of Kühlungsborn and Collm, evidence is obtained that a quasi-biennial wind oscillation similar to that known in the stratosphere and lower mesosphere seems to exist also in the mid-latitude lower thermosphere (90–95 km). Its mean period, however, is only 22 months there, in contrast to the average value of 32 months found for altitudes below 60 km in the years 1962–1969 ( Groves, 1973).