Ion temperature in the outer ionosphere — first version of a global empirical model Original Research Article

The data set of the ion temperature (Ti) recently derived from the retarding potential analyzer (RPA) volt ampere characteristics measured during the ACTIVE mission (Intercosmos 24, perigee 500 km, apogee 2500 km, inclination 83°, time period 1989–1993) was used to study the global distribution of Ti at solar maximum. The first version of a global empirical model has been constructed for altitude levels of 550, 900, and 1500 km, local time and ±90° latitude. At these fixed altitudes T; was 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 IRI (International Reference Ionosphere) shows a good agreement at the altitude of 550 km. Above 1000 km IRI shows higher Ti values during the day and lower Ti during the night. Behavior of model ion and electron temperatures is discussed.