Data on day-time and night-time radio wave absorption (at oblique and vertical incidence) in the frequency range 50 to 2614 kHz, obtained in long-term observational programmes in Central Europe, are compared with the corresponding absorption values calculated from electron density profiles of the International Reference Ionosphere (IRI-1979), for the geographic latitude 54°N. Full-wave and phase-integral methods were used, the necessary collision frequency data being deduced from the CIRA 1972 neutral pressure profiles. The observed seasonal variation of the noon absorption values at lower solar activity (R = 1o) is generally well reproduced by the corresponding IRI-profiles. Discrepancies between calculated and observed absorption values, however, were found for the diurnal and the solar-cycle variation.

Technical Report

National Environmental Satellite and Data Information Service (NESDIS)