抄録
The current wedge that forms during substorms is associated with significant magnetic field (B) changes and particle injections observed at synchronous orbit. Here it is argued that the B changes associated with the current wedge lead to a distortion of the separatrix between open and closed field lines that extends from the ionosphere to at least x=-22Re in the tail. It is suggested that the distortion forms the auroral bulge observed in the ionosphere during the expansion phase of substorms and that it causes the plasma sheet to expand at longitudes within the current wedge and to thin at longitudes near, but outside, the current wedge. A number of important substorm phenomena observed in the tail beyond synchronous orbit can be interpreted to be a result of the distortion of the separatrix. These include plasma sheet thinning and concurrent enhanced strethcing of B after expansion phase onset, plasma sheet expansion that follows thinning and should be concurrent with a field depolarization, and tailward plasma flows and associated negative Bz's during some expansion phases. The above phenomena are expected to occur at longitudes outside the current wedge that forms at onset. At longitudes within the initial current wedge, dispersionless particle injection and concurrent dipolarization of B is expected at onset as has recently been observed out to x=-22Re.
