Probe electric field measurements near a midlatitude ionospheric barium release

Abstract

A double-probe measurement of midlatitude ionospheric electric fields was made on a rocket flight near a large, artificial, barium plasma cloud. The measurement was made after ground sunset on February 1, 1971, near L = 1.8, 7 min after the release of the barium and 4 min before the visual onset of its striations. The cloud-associated perturbation of the approximately 4-mv/m electric field in an earth-fixed frame of reference was in agreement with theoretical expectations based on the enhancement of the Pedersen conductivity produced by the cloud and lends support to the gradient drift instability model of striation formation. The motion of the leading edge of the barium cloud was consistent with that expected from the rocket electric field measurement. The ionospheric electric field in a frame of reference not rotating with the earth differed from the corotation electric field by about 20% during the flight.