Variation of F-Region Positive Ion Density with Solar Activity

Abstract

Rates of production of positive ions N₂⁺, N⁺, O⁺, O₂⁺; and NO⁺ by photoionization and other chemical reactions have been calculated in the altitude range 120-400 kin for three different levels of solar activity. These levels of solar activity are characterized by three representative values of solar radio wave flux at 10·7 cm (2800 MHz) as 75, 175 and 275 W/m^-2 Hz-^-1 respectively, covering the entire range of observed values. Variations of the flux of the solar, extreme ultraviolet radiation incident upon the atmosphere, neutral particle densities, electron density and temperature, with solar activity have been taken into account. Equilibrium concentrations of all the ionic species have been calculated using laboratory measured values of the rate coefficients of ion-neutral reactions. Computed ion density profiles have been compared with the observed data.