Sensitivity of equatorial mesopause temperatures to the 27‐day solar cycle

Abstract

Night‐time observations of OH(3–1) rotational temperatures with SCIAMACHY (SCanning Imaging Absorption spectroMeter for Atmospheric CHartographY) on Envisat are used to study the sensitivity of equatorial mesopause temperatures to the 27‐day solar forcing. Fourier and cross‐correlation analysis are first used to demonstrate the presence of a solar‐driven 27‐day cycle in OH rotational temperatures. The temperature sensitivity to solar forcing is quantitatively evaluated based on a superposed epoch analysis that also demonstrates that the solar signal in the OH temperature time series is significant at the 99.9 % confidence level. The most remarkable result is that the temperature sensitivity to solar forcing in terms of the 27‐day solar cycle ( β F10.7 = 2.46 (±0.93) K/(100 sfu)) agrees within uncertainties with the majority of published sensitivity values in terms of the 11‐year solar cycle. This implies that the same underlying physical mechanism drives the mesopause temperature response to solar variability at both the 27‐day and the 11‐year time scale.