A test of the International Reference Ionosphere using single-frequency A1 data

A1 absorption and virtual reflection height data recorded at Camden, Australia during the period February 1980–January 1981 were compared with values calculated using the latest version of the International Reference Ionosphere—IRI 79. Systematic differences of 10–25 dB in absorption and 2–4 km in virtual height indicate that the IRI electron densities are too high for the lower ionosphere. A better fit between theory and experiment at Camden may be achieved by extending the top altitude of the D-region (i.e. the IRI parameter HDX) and by using a different profile shape to connect the D-region to the peak of the E-region.