Comparison of the midlatitude model with low-latitude ion composition data

Comparisons of the midlatitude ion composition model (Danilov and Smirnova, 1994) developed for IRI with low-latitude ion composition measurements are presented. The comparison demonstrates, that the model by Danilov and Smirnova (1994) quite satisfactorily represents the ratio phi(+) of the two principal molecular ions NO+ and O-2(+) at altitudes 110-170 km. Some correction of phi(+) is probably needed for altitudes h < 100 km, but there are still very few data for the D-region ion composition at low latitudes. The comparison shows also that the daytime experimental values of the O+ relative concentration R(O+) at altitudes 170-240 km exceed the model ones. A correction of the midlatitude R(O+)-profiles by 20-25% is needed. At night both phi(+) and R(O+) experimental values are higher than the ones in the Danilov and Smirnova (1994) model for chi = 90degrees, which demonstrates a need to create a comprehensive model for night-time conditions. (C) 2003 COSPAR. Published by Elsevier Science Ltd. All rights reserved.