Responses of Multiday Oscillations in the Nighttime Thermospheric Temperature to Solar and Geomagnetic Activities Measured by Fabry‐Perot Interferometer in China

Abstract

AbstractThe nighttime thermospheric temperature (~250 km) measured by FPI (Fabry‐Perot interferometer) at Xinglong (40.2°N, 117.4°E) station from 2010 to 2018 is used to investigate the responses of the multiday oscillations (periods of 27, 13.5, 9, and 7 days) in thermospheric temperature to oscillations in F10.7 and Ap index. The results show that (1) the 27‐, 13.5‐, 9‐, and 7‐day oscillations in the thermospheric temperature depend on solar phases. The 27‐day oscillations are predominant during solar maximum, while the 13.5‐, 9‐, and 7‐day oscillations are significant during solar ascending phase, and (2) the 27‐day oscillations in the thermospheric temperature are highly correlated (correlation coefficient >0.8) with the F10.7 and Ap index. Especially during solar maximum phase, the high‐correlation occurrence rate between the thermospheric temperature and F10.7 (Ap index) is up to 278.5 (191.0) days per year; (3) the 13.5‐, 9‐, and 7‐day oscillations are highly correlated with Ap index during the solar descending phase; and (4) the phase lags corresponding to the largest high‐correlation occurrence rates are mostly about 0.1π during specific solar phase.