Generation of large‐scale regions of auroral currents, electric potentials, and precipitation by the divergence of the convection electric field

Abstract

It is shown that discontinuities in the magnetospheric convection electric field E with ▽ · E <0 can generate large‐scale regions (of the order of 100 km in width) of magnetic field‐aligned currents with associated field‐aligned electric potential differences and electron precipitation of the magnitudes and widths observed in auroral regions. Such an electric field discontinuity is known to exist along the evening boundary between sunward and antisunward convection. In addition, such discontinuities may also exist over the polar cap, on account of inhomogeneities in the magnetosheath flow and in regions, such as the Alfvén layer, where drifting trapped particles charge separate. The present analysis assumes that the field‐aligned current is governed by the free particle motion in dc electric and magnetic fields, and nothing is assumed to inhibit this free particle motion.