Mini-review on topside sounding

Abstract

Ionospheric sounders flown on satellites have returned a wealth of global information of the electron density distribution from the <tex xmlns:mml="http://www.w3.org/1998/Math/MathML" xmlns:xlink="http://www.w3.org/1999/xlink">F</tex> -region electron peak upwards, not obtainable in any other way. This mini-review outlines the techniques used to obtain topside ionograms and reduce them to electron profiles, indicating the most important differences between ground-based and satellite-based ionograms. An attempt has been made here to indicate the most essential features, with the details provided in the cited references.