Variations of the upper atmosphere air density and electron density during geomagnetic disturbances

The variations of the upper atmosphere air density during geomagnetic disturbances have been investigated by many authors. According to the analysis of satellite orbits, in most cases an increase in the air density may be observed when the indexA _phas a maximum. Having ionospheric data from stations in Europe, Asia and Australia we might be able to study the global behaviour of the electron density in theF ₂ region during such geomagnetic disturbances when an increase of the air density had been observed. In these cases we found, that at the peak of the ionospheric layer, the electron density decreased 0–3 days later than theA _pmaximum.