New Vary-Chap profile of the topside ionosphere electron density distribution for use with the IRI model and the GIRO real time data

Abstract

A new Vary-Chap function is introduced for the empirical modeling of the electron density N(h) profile in the topside ionosphere that uses a shape function S(h) in the generalized Chapman function. The Vary-Chap profile extends the bottomside profile that is specified by the IRI model or measured by the Global Ionospheric Radio Observatory (GIRO) to the altitude of the ISIS-2 satellite. Some 80,000 topside profiles, measured by the topside sounder on the ISIS-2 satellite were analyzed, and the shape function S(h) was calculated for each profile. A parameterized function S*(h), composed of two sub-functions S 1(h) and S 2(h), is fitted to the measured S(h) profile using three free parameters. At altitudes just above the F2 layer peak height hmF2, the shape function S 1 controls S(h), and at greater altitudes S 2 controls S(h). The height of the intersection of S1 and S2 is defined as the transition height h T indicating the transition from an O + to an H +-dominated profile shape. The observed transition heights range from ∼500 km to 800 km. Copyright 2012 by the American Geophysical Union.