COMPARISON OF A LOW-LATITUDE IONOSPHERIC MODEL WITH OBSERVATIONS OF 01 630 nm EMISSION AND IONOSPHERIC PARAMETERS

A comparative study is carried out between a semi-empirical low-latitude ionospheric model (SLIM). including calculated 01 630 nm airglow emission intensities predicted by the SLIM model, with ionospheric and r>I 630 nm airglow measurements carried out at Cachoeira Paulista (22.7”S, 45.O”W; geomag. 11.9”S), Brazil. A long series of regular measurements of ionospheric F-region peak electron densities and peak heights, and regular zenith measurements of the 01630 nm airglow emission intensities, made during the period 1975-1982, are used for comparison with corresponding parameters predicted by the SLIM model. Large discrepancies between the observed and model-predicted 01 630 nm intensities have been found for high solar activity, mainly due to an overestimate of the F-region peak heights by the SLIM model. Use of SLIM profiles normalized by actual F-region peak height and density observations essentially removed the disagreements. The reasons for the height discrepancies are discussed in terms of the longitudinal dependence of the geomagnetic control on the ExB vertical plasma drifts and the thermospheric neutral wind effects on the F-region. The effects of the magnetic declination angle on both the E x B ionospheric plasma drifts and thermospheric neutral winds at low-latitude suggest that ionospheric models need to address separately the longitudinal zones of magnetic declination either positive, negative or zero.