Investigation of the daytime lower ionosphere over the equator using Langmuir probe and plasma noise probe

Abstract

A Langmuir probe and plasma noise probe payload launched from Thumba on 29 August, 1968 at 1415 hr IST explored the equatorial D-region above about 60 km. The electron density profiles obtained from the Langmuir probe currents do not show any pronounced layering in the D-region. They exhibit a steep rise below 70 km and above about 85 km while in the intermediate region the slope is relatively small. These profiles are compared with two other electron density profiles available in literature for the equatorial lower ionosphere. Most of the observed differences are found to be explicable in terms of the difference in solar activity prevalent when these profiles were obtained. A comparison was also made with two electron density profiles obtained at similar conditions of solar activity and for similar solar zenith angles, but over the middle latitudes. No marked differences between the equatorial and middle latitude profiles could be observed. The plasma noise probe measured the electron density irregularities in the scale size range 1–15 m present in the medium. Irregularities were found to be present almost throughout the height region 65–105 km, with amplitudes ranging from a few tenths to a few percent. The results are compared with other available results on the electron density irregularities obtained using different techniques.