• mesopause temperature;
  • satellite remote sensing;
  • solar variability

[1] 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 (βF10.7= 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.