Outstanding issues of ring current dynamics

The terrestrial ring current consists of energetic charged particles flowing toroidally around the Earth, and creating a ring of westward electric current, centered at the equatorial plane and extending from geocentric distances of about 3-8R(E). Changes in this current are responsible for global decreases in the Earth's surface magnetic field, which is the defining feature of geomagnetic storms. The ring current is a critical element in understanding the onset and development of space weather disturbances in geospace. This review paper discusses recent developments in ring current research, and outlines the presently hottest issues, most of which were addressed at the Ring Current Symposium of the First S-RAMP Conference held in Sapporo, Japan, in October 2000. (C) 2002 Elsevier Science Ltd. All rights reserved.