Measurements of Electron Number Density in the Polar Ionosphere

Abstract

Under the projects of the IMS, the Japanese Antarctic Research Expedition parties carried out sounding rocket observations using the S-210JA and S-310JA rockets. The swept frequency impedance probe (NEI), which is canable of making in situ measurement of the ionospheric electron number density, within an error ±3%, was installed on the rockets co-ordinately with various other instruments. In the polar ionosphere, ionospheric parameters such as the number density of electron and the electron and ion temperatures are highly variable in time and space. The investigation of the physical processes in this region requires, therefore, accurate in situ observation of the ionospheric parameters. The electron number density profiles up to 221 km altitude were obtained by the NEl installed on the S-310JA-3 rocket, launched at 18 : 35 (45° EMT) on July 26, 1977. The ionospheric layer with the peak density of 1.0-2.6×10^4 electrons/cm^3 and with the altitude width of about 20-30 km was observed around an altitude of 100 km.