Ionospheric specification with analytical profilers: Evidences of non-Chapman electron density distribution in the upper ionosphere

• Topside ionospheric profilers investigated for suitability under different conditions.
• Ionospheric characteristics can provide reliable criteria for selecting a suitable profiler.
• Chapman profilers should not be used indiscriminately in ionospheric modelling.

In relation to the development of an operational ionospheric monitoring and imaging system, the most frequently used analytical ionospheric profilers (Chapman, Epstein, Exponential) were investigated in terms of suitability for topside ionosphere modelling. For the purpose, topside sounder measurements onboard Alouette and ISIS satellites have been analysed. We have come to the conclusion that the use of the Chapman profiler should be exercised with precaution as there are evidences that there are conditions when other profilers are better fit for modelling purposes. This is highlighted during ionospheric disturbances (e.g. during geomagnetic storms), when the shape of the topside electron density distribution might be better described by an Epstein profiler rather than a Chapman profiler.