Electric fields in the equatorial ionosphere

Abstract

During a Commonwealth Collaborative Campaign between India and the U.K., artificial ion and neutral clouds were released at altitudes between 150 km and 160 km, using Petrel rockets launched from the TERLS range, Thumba, India. The experiments were conducted at local dusk, and the magnitude of the electric field components and neutral wind velocities were deduced from the motion of the ionized and neutral artificial clouds. The values obtained, E ∼ 3 mV/m and v n ∼ 80 m/sec, are in reasonable agreement with those reported in the literature from earlier experiments performed near the geomagnetic dip equator. Although the electric field was measured when the electrojet current, as inferred from ground based magnetometers, was very small, information about the electrojet current system can be obtained from an inspection of the ratio of the vertical to the east-west components of the electric field. This ratio is much greater than that of the local Hall to Pedersen conductivities, and is closer in value to the ratio of the integrals of the Hall and Pedersen conductivities performed along the geomagnetic field lines. This confirms the validity of the electrojet model proposed originally by Untiedt (1967), in which some currents flow perpendicular to the geomagnetic lines of force.