LAUSR

Abstract An increasing body of evidence supports the conclusion that electrical variations in the Polar Regions influence atmospheric radiative properties. These influences can be transmitted (1) by the global electric circuit from remote thunderstorms and electrified shower clouds; (2) from local electric fields associated with ionospheric currents that generate magnetic activity, and (3) from local penetration of the solar wind electric field. A regression-based analysis reveals a positive relationship between downwelling longwave radiation observed during the dark portion of the year at the South Pole and the vertical electric field measured at the Antarctic stations Vostok and Concordia from 1998 to 2011, component (1). An increase in the electric field of 22.4 Vm-1, equal to one standard deviation of the nighttime mean, is followed one day later by a longwave irradiance 2.78 ± 1.90% larger than would exist otherwise. In addition, a significant negative correlation with a lag of two days exists between longwave irradiance recorded from late 1993 to mid-2017 and the Ap index, which measures temporal variations in the surface magnetic field associated with electric fields of ionospheric origin, component (2). There is a weaker, less-definitive, positive correlation of longwave irradiance with the interplanetary magnetic field index By which is associated with the solar wind electric field, component (3). These results are consistent with previous work using visible radiation, and with the hypothesis that the ionosphere-earth current density influences the microphysics of polar clouds, with consequences for radiative processes and meteorological variables such as surface pressure.