抄録
Our present knowledge about the coupling between the neutral and the ionized upper atmosphere during disturbed conditions is reviewed. The idea that negative ionospheric storms are caused by changes in the neutral gas composition is now well established. The expansion of the composition disturbance is restricted to the midnight/early morning sector, leading to significant local time effects. Positive ionospheric storms are attributed to transport of ionization. It is argued that this transport is affected by meridional winds. Both traveling atmospheric disturbances and changes in the global wind circulation will contribute to the perturbations.
