What is space weather?

Space weather refers to the dynamic, highly variable conditions in the geospace environment including those on the sun, in the interplanetary medium, and in the magnetosphere-ionosphere-thermosphere system. Adverse changes in the near-Earth space environment can diminish the performance and reliability of both spacecraft and ground-based systems. This, in turn, can spell major losses due to communication, navigation, power system, and reconnaissance satellite operational problems. This paper discusses some of the principal adverse space environmental effects presently known including trapped magnetospheric radiation, solar energetic particles, geomagnetic storms, and magnetospheric substorms. The scientific underpinnings for present prediction methods in space weather are considered. It is concluded that practical and effective methods of predicting and mitigating space weather effects are close at hand. (C) 1998 COSPAR. Published by Elsevier Science Ltd. All rights reserved.