On some determinations of the sign and magnitude of electric discharges in lightning flashes

Abstract

The Sign and magnitude of the electric transferred from the atmosphere to the earth in lightning flashes are of interest, not only in themselves, but also as having to be taken into account in any attempt to test whether there is a balance in the interchange of electrical charges between the atmosphere and the surface of the earth. As is well known, the evidence at present available appears to show that on the whole an excess of positive electricity passes from the atmosphere to the earth as a result of conduction by ions and convection by charged raindrops. I am not aware of the existence of any data on which more than the roughest estimate of the magnitude of lightning discharges could be based. Schuster, starting with two determinations by Pockels of the maximum current, measured by means of its magnetising effect, and taking 1/1000 second as the duration of a flash, estimates the quantity brought down by a discharge as about 10 coulombs.