Solar Wind Modulation of the Global Electric Circuit and Apparent Effects on Cloud Microphysics, Latent Heat Release, and Tropospheric Dynamics

Abstract

The solar wind modulation of the energy distribution and flux of galactic cosmic rays causes 11 year cycles in the latitude distribution of air-earth current density in the global electric circuit. Similar changes occur with solar activity on the day to day time scale. At least 3 independent data sets correlate changes in tropospheric winds and vorticity with measured and modelled changes in air-earth current density in the troposphere. These are (1) the decadal oscillations in winter in the North Atlantic region, with period averaging 11 ± 2 years over the last 120 years, and which appear to have been phase locked to the solar cycle except for a period of generally low solar activity prior to 1925; (2) the decrease in 500 mbar Vorticity Area Index (VAI) in winter at times of Forbush decreases of cosmic ray flux; and (3) decreases of 500 mbar VAI in winter at times of solar wind magnetic sector boundary passages, when volcanic aerosols from Agung and El Chicon were in the global stratosphere, together with solar wind sector modulated relativistic electron precipitation. One possible physical mechanism connecting changes in air-earth current density with changes in tropospheric dynamics is via the accumulation of electrostatic charge at cloud tops affecting the microphysics of ice nucleation and precipitation, with consequences for latent heat release and the intensification of winter cyclones.