Westward cross-tail current at the earthward edge of the plasma sheet is enhanced due to strongly stochastic (rLi~Rc) ion motions. A narrow elongated magnetic field depression arises which leads to further stochastication of the ions convecting through it, and to a local increase of magnetostatic plasma pressure, enhanced lateral transport and removal of higher energy ions. This plasma structure can be stationary in the magnetospheric frame.

It is the ''root'' of sheet-like auroral currents of stable auroral homogeneous arcs/bands (inverted-V's) located at the equatorial edge of the steady premidnight auroral oval. The magnetic field minimum can be the location of a sub-storm onset when it deepens below the stability threshold for reconnection/tearing. ¿ American Geophysical Union 1992