The polar thermospheric temperature behavior during the 11‐year solar cycle

Results of neutral temperature measurements in the polar thermosphere between 1968 and 1976 show a large variation as a function of the solar cycle. A very cold thermosphere associated with a high altitude for the mesopause is found at the maximum of solar activity. The amplitude of variation of neutral temperature at 165 km is 500°K, and the mesopause is observed to move from 120 to 90 km. Those results are attributed to the variation of both the amplitude and the altitude of turbulent processes as a function of solar activity. Theoretical calculations and experimental facts are in support of that explanation.