SOLAR-CYCLE EFFECTS ON THE NEAR-EARTH SPACE ENVIRONMENT

Forecasts of the magnitude of solar activity in the 1990s (solar cycle 22) imply that the expected levels of activity might be some of the most extreme ever recorded, and almost certainly the levels of activity will be the highest experienced during the space age. Even as early as 1 year before the expected maximum of solar cycle 22 in 1990, unprecedented levels of solar activity (for example, the solar flares and solar particle events of August–October 1989) and geomagnetic activity (for example, the auroral events and geomagnetic storms of March 1989) have been observed. These solar and geophysical events have stirred scientific interest both in the long‐term behavior of solar activity and in the physics which couples the energy of solar events to the near‐Earth environment. Furthermore, the operational community (including those involved in satellite operations, telephone and radio communication, electric power distribution, aviation, and others) have experienced many adverse effects of these solar and geophysical events. Many more episodes of activity are expected throughout the upcoming 4–5 years. The purpose of this paper is to review the direct and indirect influences of solar activity on the near‐Earth environment and to describe some of the implications of the high levels of solar activity which are expected to occur in the 1990–1994 time period. Copyright 1990 by the American Geophysical Union.