Rocket Observations of Electron Density and Temperature Profiles in the Auroral Ionosphere

Abstract

Six profiles of electron density and temperature under quiet daytime and disturbed nighttime ionospheric conditions were observed by the sounding rockets launched in 1976 from Syowa Station. It is found that the daytime electron density profiles have a solar zenith angle dependence and that the nighttime ones are dependent on auroral activity levels. Enhancement of the electron density amounting to 2-5×10^5/cm^3 was observed in the E-region when a rocket penetrated aurora. The electron temperature in the E-region was within 500-900 K, increasing with altitude, whereas that in the nighttime was within 700-1000 K, decreasing with altitude. The latter fact may indicate that heat source exists around 100 km in altitude during distrubed condition. Some discussions are made on the twenty-two electron density profiles obtained during 1970-1976 to summarize the characteristic feature of the auroral ionosphere. Finally, the empirical formulae are deduced to infer the nighttime electron density during a large substorm from the 30 MHz cosmic noise absorption and geomagnetic disturbance levels.