Local Characteristics of the Electron Temperature Profile

The third Japanese scientific satellite “TAIYO”: has accomplished the first ten month mission during a period of minimum activity of the sun. The onboard electron temperature probe worked perfectly during this mission, obtaining the distribution of electron temperature in the height region from 250 km to 3,000 km in the low latitude of ±31 degrees. The solar radio flux as well as the sunspot number was almost constant and low except for some enhancement especially in August 1975. Therefore, the electron temperature was also quite stable and showed regular characteristics in time and space without being disturbed by the geophysical disturbance. In the present paper, the orbital variation of electron temperature is carefully examined. Also, the mean electron temperature profiles in the nighttime at some particular localities are discussed. Among them, the profiles obtained in the geomagnetic South Atlantic anomaly region show a remarkable temperature gradient in both the ionosphere and protonosphere. These anomalous distributions of electron temperature suggest close coupling of the protonosphere and the ionosphere in this anomaly region.