An improved phenomenological model of ionospheric density

Abstract

A global representation of the large scale variations of ionospheric electron density with the annual, diurnal and solar activity cycles is described. The phenomenological model, requiring minimal computer storage space, is constructed from monthly-averaged hourly ionospheric sounding data from some 50 stations during the epoch 1957–1970, as provided by World Data Center (A). The model, describing noontime F2-layer critical frequencies to better than 2 MHz average maximum error and to better than 0.5 MHz root mean squared error, is particularly suitable for applications in space communication and ionosphere-atmosphere coupling studies. Magnetic dip angle and north-south asymmetry effects are incorporated in the model. We show that a ‘secular’ variation of the ionospheric density exists in the epoch 1960–1971. The basis of comparison with data is broadened to include the 1958–1968 chronologies of 18 stations in addition to the original samplings of 50 stations. In addition, a modelling of the polar ionospheres is included.