Geophysical disturbance effects on the state of the propagation medium and their predictability

Different types of disturbances in the upper atmosphere can change its properties as a propagation medium for electromagnetic waves. The most important of these disturbances are reviewed along with the possibility of predicting, not their actual occurrence, but rather their effect on the atmosphere once they have occurred. The review is based upon current knowledge of ionospheric and upper atmosphere physics, and concentrates on effects of importance to radio wave propagation. Both natural phenomena, such as magnetic storms, and man-made disturbances are discussed.