RELATIONSHIP BETWEEN LARGE HORIZONTAL ELECTRIC-FIELDS AND AURORAL ARCELEMENTS

High time resolution optical measurements in the magnetic zenith are c ompared with European Incoherent Scatter (EISCAT) field-aligned measur ements of electron density at 0.2-s resolution and with horizontal ele ctric field measurements made at 278 km with resolution of 9 s. In one event, 20 min after a spectacular amoral breakup, a system of narrow and active are elements moved southward into the magnetic zenith, wher e it remained for several minutes. During a 30-s interval of activity in a narrow are element very close to the radar beam, the electric fie ld vectors at 3-s resolution were found to be extremely large (up to 4 00 mV m(-1)) and to point toward the bright optical features in the ar c, which moved along its length. It is proposed that the large electri c fields are short-lived and are directly associated with the particle precipitation that causes the bright features in auroral are elements .