Outstanding issues in understanding the dynamics of the inner plasma sheet and ring current during storms and substorms

The paper dears with five selected issues of the dynamical coupling of the near-Earth plasma sheet and magnetosphere, (1) substorm initiation, (2) dipolarization, (3) pressure release of the outer magnetosphere via the auroral energy conversion process, (4) magnetization of the very high beta plasma assembling at the inner edge of the tail, and (5) penetration of energetic particles into the ring current below L congruent to 4. One outstanding and strongly debated subject is not discussed here, the origin of the substorm current wedge. The main conclusions (or personal preferences) are: (1) the substorm is initiated by formation of a near-Earth neutral line; (2) dipolarization occurs through magnetic flux transport by the earthward reconnection flow and not by current diffusion; (3) the auroral energy conversion process, the "auroral pressure valve", contributes substantially to the pressure release during the substorms; (4) high beta (>> 10) plasma breaks up into smaller scale blobs under slow magnetization; and (5) deep and prolonged penetration of hot plasma sheet plasma into the middle ma,magnetosphere produces currents and electric fields which lead to the growth of the storm-time ring current. (C) 2000 COSPAR. Published by Elsevier Science Ltd.