Velocity filter effect and dynamics of distant magnetotail

Abstract

The velocity filter effect produces a persistent time variation of the self-consistent magnetic-field configuration in the Earth's distant magnetotail. In the presence of a mantle source of plasma, a steady-state configuration cannot be attained, even if the source supply is constant in time. The velocity filter effect produces an evolution of the magnetotail such that the plasma sheet thins throughout the region accessible to the incoming plasma. This thinning process, widely observed and theoretically predicted, leads to current-sheet disruption when the thickness of the plasma sheet shrinks to a critical value. The whole process lasts 1–2 h, consistent with the observed duration of a typical substorm growth phase.