GRUAN Radiosoundings for Ionospheric Potential
1 September 2022 - 30 April 2024
Lead Scientist: Earle Williams
The line integral of the atmospheric electric field in fair-weather conditions, from the conductive Earth to the conductive upper atmosphere (stratosphere), is the “ionospheric potential”, Vi, with nominal magnitude ~240 kilovolts. Vi is a global invariant, and characterizes the integrated electrical activity of thunderstorms and electrified shower clouds of the DC global electrical circuit. In this study, balloon-borne electric field sensors will be used to measure Vi simultaneously from two widely separated island sites: the ARM site at Graciosa Island in the Atlantic Ocean and the GRUAN site at Lauder in New Zealand in the Pacific Ocean. A pair of soundings at both locations will take place roughly once per month when African lightning is dominant (14-15 UT) and when American lightning is dominant (19-20 UT). The scientific motivation for these measurements is aimed at the “global circuits paradox”: the evidence that the DC global circuit is maximum when the American lightning is dominant, and the AC global circuit (aka, Schumann resonances) is often dominant when Africa is most active. Hypotheses to resolve the paradox involve electrified shower clouds (moist convection devoid of lightning) and cloud condensation nuclei at cloud base height (measurable from satellites in space), both of which differ between Africa and America, and will be monitored on days selected for the balloon soundings. A longer-range goal is the development of an instrument for operational monitoring of Vi for climate change.