On the noon asymmetry of the diurnal variation of radio wave absorption

Summary The assymetry of the diurnal variation of radio-wave ionospheric absorption, measured by the A3 method on the 2775 kHz Kiel — Panská Ves circuit, is studied. Almost full symmetry of absorption is observed in winter and autumn. It is explained by electron concentration variations. A remarkable diurnal asymmetry of absorption is observed in spring and particularly in summer. The observed diurnal asymmetry of the electron concentration seems to be insufficient to account completely for the great absorption asymmetry observed.