Seasonal and Solar Wind Sector Duration Influences on the Correlation of High Latitude Clouds With Ionospheric Potential

Irradiances from long-lived stratus-type clouds at Alert (Canada), Summit (Greenland), and South Pole, previously measured, show correlations with the day-to-day input to the global atmospheric electric circuit from the solar wind, as well as with the inputs of low- and mid-latitude thunderstorms and shower clouds. We analyze the measured Alert cloud irradiances, and find differences in the responses to 2, 4, or more solar wind sectors per 27-days solar rotation. We find seasonal variations in the correlations, with sign reversal in the summer. The correlation coefficients that were found previously for all-year, all sector types show further increases for just winter months and in addition, for just 2-sector intervals. At high magnetic latitudes, the ionospheric potential correlates strongly with the solar wind sector structure, and determines the flow of current density (J_Z) to the Earth's surface that passes through clouds and modifies space charge in them. Parameterizations of the potential distribution near the magnetic pole are used in the correlations. The daily average values depend mainly on the solar wind (interplanetary) magnetic field (IMF) B_Y component, with lesser influence of the solar wind speed and IMF B_Z. Mechanisms by which space charge in clouds can affect cloud microphysics and cloud opacity are described and are qualitatively consistent with the correlations, but need quantitative testing.