Point discharge current, the earth's electrical field and rain charges during disturbed weather at Poona

Abstract

An analysis of ,measurements of the current flowing to earth through an insulated point set up at the Meteorological Office, Poona, at a height of 17.8 metres together with simultaneous measurements of potential gradient by a quick-run photographic electrograph during fourteen thunderstorms in 1955 show that point discharge currents of either sign; can be represented a~ increasing with the square of the field as found by Whlpple and Scrase for Kew, Hutchmson for Durham, Chlplonkar for Colaba (Bombay). An advancement of the field change ahead of the corresponding point discharge current is shown during a few thunderstorms at Poona like the one noticed by Hutchin~on for Dllrham. A comparison of point discharge current measurements with field strength at Poona taken typical of tropical region and Kew (taken typical of temperate region) show that there is no major difference in the electroal conditions in the tropical and temperate regions. Simpson's 'mirror image' effect is also shown by Poona records but the syncbronization of the change in the sign of the rain current is more with the field change rather than with the point discharge current which lags behind the field change, Preliminary results with four-point discharger show that the total current is more than the current from a similar single point for the same field.