QUASI-BIENNIAL OSCILLATION IN IONOSPHERIC PARAMETERS MEASURED AT JULIUSRUH (55-DEGREES-N, 13-DEGREES-E)

When seasonal variations were eliminated by evaluating 12-month runnin g means, the ionospheric parameters foE,foF2 and hmF2 at Juliusruh (54 .6 degrees N, 13.4 degrees E) showed large solar cycle variations. How ever, when further 3-yr running averages were evaluated and subtracted , QBO (Quasi-biennial oscillations) were noticed in all these paramete rs. Sunspot series did not reveal a QBO, but geomagnetic Ap did show a QBO. The peaks of the ionospheric QBO and QBO of Ap could be roughly compared, with lags or leads of a few months. Also, these compared rou ghly with the well-known QBO peaks of tropical stratospheric (50 mb) z onal winds. Similar analyses at other locations are warranted.