Upper-atmospheric effects of magnetic storms: a brief tutorial

The physical processes underlying several phenomena of upper-atmospheric storms are described: magnetospherically driven ion convection and Joule heating and their impact on the high-latitude thermosphere and ionosphere; global changes in thermospheric circulation and composition; traveling atmospheric disturbances; and effects of electric-field penetration to middle and low latitudes. Examples from the 1997 January 10-11 storm are used to illustrate some of these features. It is pointed out that not only the magnitude, but also the sign of many storm-time changes at any given location depend sensitively on the temporal and spatial variations of auroral particle precipitation and high-latitude electric fields. In order for simulation models to be able to predict upper-atmospheric storm effects accurately, improved determination of the high-latitude inputs will be required. (C) 2000 Elsevier Science Ltd. All rights reserved.