Abstract
The substorm‐related thinning and thickening of the plasma sheet, processes that have been extensively studied at XSM≈ −18 RE, occur at all distances in the magnetotail beyond XSM ≈ −10 to −15 RE in most substorms. These processes involve rapid flow of plasma out of and into the magnetotail and suggest the formation of magnetic neutral lines, first near the earth and then far out in the tail during a substorm. Evidence for these processes is discussed.