Altitude variations of middle-latitude topside ionospheric electron-density profiles Original Research Article

An approach to determine the dependence of the mid-latitude topside ionospheric electron number density (Ne) altitude distributions and ion composition changes on long-term solar-cycle variations and short-term solar-wind and magnetic disturbances has been developed. This approach focuses on Ne altitude profiles from the height of the ionospheric Ne maximum to ∼3000 km as deduced from ISIS (International Satellites for Ionospheric Studies) topside-sounder data. These data, obtained over a two-decade time interval, can be used to investigate secular changes in the topside Ne profiles, which reflect altitude changes in plasma temperature and ion composition, over more than a solar cycle. The approach is to determine the locations of mid-latitude O+/H+ transition altitudes deduced by fitting the topside Ne profiles to modeled H+ and O+ profiles using the base electron temperatures and constant temperature gradients as variables.