Climatology of ionospheric drift perturbations at Collm, Germany Original Research Article

The observations of the intensity of drift velocity perturbations with periods 0.7 – 3 hours are presented for altitudes of 80 – 110 km obtained with the D1 method at Collm, Germany (52° N, 15° E) during 1983 – 1999. Seasonal variations of perturbation intensity show different behavior at altitudes below and above 100 km. Interannual changes of perturbation intensity reveal a maximum in 1989 – 1993, which is correlated with changes of the mean winds measured at Collm. Experimental results are consistent with model calculations of propagation of a gravity wave spectrum in the middle and upper atmosphere.