The 27-day solar rotational cycle response in the mesospheric metal layers at low latitudes

To investigate the response of the meteoric metal layers in the mesosphere and lower thermosphere region to the 27-day solar rotational cycle, a long-term simulation of the Whole Atmosphere Climate Community Model (WACCM) with the chemistry of three metals (Na, K, and Fe) was analysed. The correlation between variability in the metal layers and solar 27-day forcing during different phases of the solar 11-year cycle reveals that the response in the metal layers is much stronger during solar maximum. The altitude dependent correlation and sensitivity of the metal layers to the solar spectral irradiance demonstrates that there is a significant increase in sensitivity to solar rotational cycle with increasing altitude. Above 100 km, the sensitivity of the metals to changes of 10% in the SSI at Lyman-alpha is estimated to be -5%. A similar response is seen in Na layer measurements made by the OSIRIS instrument on the Odin satellite.