A study of the equatorial E-region during evening twilight using a Langmuir probe

Abstract

Langmuir probe data obtained from a rocket flight during the evening twilight of 12 March 1967 from Thumba (India) near the magnetic equator are presented. An E2 layer was seen at 130 km during ascent and 136 km during descent. The electron temperatures in the layer were larger than below the layer by a factor of 2. The increased electron temperatures may be partially due to electric currents flowing in those regions. The decrease in the recombination coefficient with the increase in the electron temperature may at least partly be responsible for the enhanced ionisation in these regions. Audio frequency fluctuations in the ambient ionised medium (ionospheric ‘noise’) were recorded in the frequency range 880 Hz (± 15 per cent). The amplitude and the type of the signal spectrum was found to vary with height. The observed noise may be due to ion acoustic waves possibly produced by winds or electric fields.