Large‐scale electric fields in the Earth's magnetosphere

Abstract

Studies of the earth's magnetosphere have indicated that a large‐scale electric field E plays a central role in its electrodynamics and in the flow and acceleration of charged particles there; while many observations relevant to E have accumulated, quite a few basic problems involving the origin and structure of this field remain unsolved. The ultimate source of E is presumably the flow of the solar wind past the earth, but the mechanism by which E arises is still unclear, and several independent sources may contribute to it, some of them (e.g., substorm fields and E 11 ) being of a rather transient nature. This review attempts to sum up the main observed facts and theoretical concepts related to E . It also contains brief sections on experimental methods and on Birkeland currents, and it concludes with a list of basic questions related to the magnetospheric electric field to which satisfactory answers have yet to be found.