Electric fields in the E region during the counter electrojet

The electron density distribution in the E region during counter electrojets is investigated. Rocket-borne Langmuir probes were flown from Thumba, India (dip 0.47 arcmin S) on August 17, 1972, a magnetically quiet day, and on April 25, a magnetically disturbed day, when ground-based magnetometers indicated a daytime decrease of the difference between equatorial and nonequatorial values of the horizontal component of the earth's magnetic field from its nighttime base level. Electron density irregularities with scale sizes from 1 to 15 m were observed in bursts in the 87 to 95 km region, and continuously with varying amplitude in the 96 to 110 km region, while 30- to 300-m irregularities with sawtooth waveforms similar to normal daytime electrojets were found in the region of downward density gradients. Results indicate that the Hall polarization fields are downwards up to 110 km, and that during counter electrojet events, electric fields reverse not only below the electrojet region, but within the main electrojet region as well