Redefining the IRI F1 layer profile Original Research Article

This paper provides a new formulation for the presentation of the F1 layer in the IRI electron density profile. Recently the bottomside F2 layer of the IRI model had been improved by searching for better parameters B0 and B1 which define the thickness and shape of the F2 layer. The work is now continued through the F1 layer to the top of the E-valley. The IRI-90 model for the F1 layer with its one free parameter, C1, is difficult to fit to actual profiles. A new functional description of the F1 layer is given in this paper that avoids the difficulties found in IRI-90 for the modeling of the F1 profile. The new F1 representation also has one free parameter, D1. The Digisonde network automatically calculates D1 in real time together with the B0 and B1 parameters. A reasonable fit is obtained by using D1 = 2.5 C1.