Lower-thermosphere temperature determined from the line profiles of the O I 17,924-K (5577 Å) emission in the night sky, 2, Interaction with the lower atmosphere during stratospheric warmings

Abstract

Interaction between the lower thermosphere, at 40°N, and the stratosphere has been found during stratospheric warming events. This interaction shows a temperature decrease of the lower thermosphere of about 10°K (with a 95% confidence interval from 4.2°K to 17°K). Cooling already occurs by the time of peak stratospheric warming; however, maximum cooling appears nearly one lunation later. The measurements show the average magnitude of the cooling effect to be independent of solar activity, magnetic activity, and other long-term secular variations to which the temperatures in the lower thermosphere are sensitive and to be independent of a 34° longitude separation in observing sites. The results indicate that the magnitude of the cooling effect may be dependent on the time of occurrence of the stratospheric warming during the winter; however, there are not enough measurements to test this contention fully.