An analytic/empirical model of the middle and low latitude ionosphere

An improved analytic/empirical model of F-layer plasma density is developed by modifying the Chiu (1975) model so as to: (a) better approximate middle latitude F-layer peak heights (hmF2's) as derived from ionosonde data, and (b) better model features such as the post-sunset rise in the F-layer peak height, and the equatorial anomaly maxima in plasma density near + or - 15 geomagnetic latitude. The latter is accomplished by applying analytic low-latitude correction as derived from differences between the Chiu model and the SLIM model of Anderson et al. Results of a numerical model are also presented that demonstrate the importance of these low-latitude plasma structures tot he neutral dynamics of the thermosphere.