Periods concerning the absorption of radio waves in the ionosphere

The absorption L of intermediate waves (1.6-3 MHz) in the lower ionosphere can be regarded as a sensitive diagnostic parameter which provides information concerning the behavior of the lower ionosphere for a period of many years. The parameter L is proportional to the integral of the product of the electron density profile and the collision frequency profile. The parameter L depends also on the form of the electron density profile. The absorption of the intermediate waves takes place in the altitude range from 75 to 120 km. The mathematical description of the diurnal characteristics of the absorption is discussed. Approaches of mean value formation are found suitable for the representation of periodicities. Computed mean periods have durations in the range from 22 to 125 days.