IONOSPHERIC ELECTRICAL CURRENTS IN THE LATE EVENING PLASMA-FLOW REVERSAL

An instrumented sounding rocket was launched from Andoya, Norway, In January 1977, in the late evening auroral oval. Its trajectory took it northward over a quiet auroral arc and over a region of plasma flow reversal. Horizontal currents were inferred from magnetic field measurements; they were also calculated from the measured electric field and conductivities derived from energetic particle influxes. South of the reversal region the sheet current density of the eastward electrojet was found to be similar 0. 1 A/m, while north of the reversal the current density was less than 0. 05 A/m. The currents were enhanced in the arc. Current continuity considerations in the meridian plane implied downward field-aligned currents at the southern edge of the arc and upward field-aligned currents at the northern edge.