Seasonal and solar wind sector duration influences on the correlations
of high latitude clouds with ionospheric potential.
Abstract
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-day 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 (Jz) 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) By
component, with lesser influence of the solar wind speed and IMF Bz.
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.