An empirical model of ion composition in the outer ionosphere Original Research Article

In an earlier paper Třísková et al. (2002) have presented a new global empirical model for the topside ion composition based on data from the Intercosmos 24 satellite (ACTIVE mission). The model provides the relative densities of the major ions (O+ and H+) for high solar activity in the altitude range 500 km to 2500 km. In the present study this model has been extended to include the He+ and N+ ion composition and to cover low solar activities. This is accomplished with the help of Atmosphere C and E data. The first order variations at four fixed altitude ranges were represented by a system of associated Legendre polynomials (up to the 6th order) in terms of magnetic local time and latitude coordinates. Comparison of the model values with the initial data and with other measurements are described in a companion paper in this issue.