NEW FEATURES OF TIME-DOMAIN ELECTRIC-FIELD STRUCTURES IN THE AURORAL ACCELERATION REGION

The Polar Satellite carries the first three-axis electric field detect or flown in the magnetosphere. Its direct measurement of electric fiel d components perpendicular and parallel to the local magnetic field ha s revealed new classes and features of electric field structures assoc iated with the plasma acceleration that produces discrete auroras and that populates the magnetosphere with plasma of ionospheric origin. Th ese structures, associated with the hydrogen ion cyclotron mode, inclu de very large solitary waves, spiky field structures, wave envelopes o f parallel electric fields, and very large amplitude, nonlinear, coher ent ion cyclotron waves.