Electrodynamic properties of the evening sector ionosphere within the region 2 field-aligned current sheet

Chatanika radar measurements were combined with magnetometer data from the Triad satellite to relate the electrodynamic properties of the ionosphere to field-aligned currents. Radar electric field and electron density were studied for eight evenings during which the region 2 (downward) field-aligned current was entirely within the radar field of view. In all cases the downward current region coincided with an E region electron density that increased to the north. The equatorward boundary of the current sheet was associatd with maximum E region densities of about 1 x 105 el/cm3. The poleward boundary of the current sheet was always characterized by a local maximum in E region ionization referred to as the interface arc. The ionospheric perpendicular current was generally northeastward within the downward current sheet. The gradient in the northward ionospheric current was used to compute field-aligned currents, which were in good agreement with those measured by Triad