176-179A balloon carrying a Langmuir probe payload for measuring the positive and negative ion densities in the stratosphere was flown around midnight IST on 23 Mar 1982 from the National Balloon Facility at Hydrabad, a low latitude station. The Langmuir probe with a guard ring arrangement is given a symmetrical probe voltage of triangular waveform with amplitude ± 4.2 V and with a repetition frequency of 0.28 Hz. The balloon reached a ceiling altitude of 33km and data were taken from 15km up to the ceiling altitude. The altitude profiles of the ion density show a peak around 18km with densities decreasing with altitude. The results are discussed in terms of cosmic ray production and ion chemistry. The structures in the positive ion density profile are interpreted in terms of the presence of aerosol layers
