| Summary: | Observations of wind and airglow brightness in the northern polar cap mesopause region using an all-sky imager (irradiance images) and a field-widened Michelson interferometer (E-Region Wind Interferometer (ERWIN) - wind and irradiance) have taken place at the Polar Environment Atmospheric Research Laboratory (PEARL – Eureka, Nu, 80 N) since 2008. These observations provide insights into solar cycle, seasonal and diurnal variations in airglow brightness and winds. The sodium and oxygen green line airglow brightness correlates strongly with the solar cycle in spite of the observation site being in polar night. The brightness varies strongly during the winter months with several peaks. The cause of this variability is not obvious. The seasonally average meridional winds are generally southward (northward would be expected based on the residual circulation) over the 12 years with maximum southward amplitudes of ~ 10 m/s in the 2014/2016 period. Seasonally averaged zonal winds are generally eastward. The monthly mean zonal winds maximize in January at 10 m/s. The monthly mean meridional winds do not vary strongly during the winter season.
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