Measurement of space charge in the lower atmosphere

Abstract

A double field mill is described which, when placed at a point abore the earth's surface, is automatically brought to the potential of that point and registers the potential gradient* Two such Instruments are employed to study space charge values In the first fire metres of the atmosphere. Comparison Is made between results obtained using the double mills and an Obolensky-type air filter, which lead to the conclusion that the latter instnuasnt gives incorrect readings in the presence of largp* small- ion concentrations. Space charge studies In fair weather conditions indicate the presence of a negative charge close to the ground of approximately -50µµC/m(^3), decreasing in the first two metres to aero and having an average value between one and three metres of +3µµC/m(^3). file average height to which this charge extends is shown to be proportional to the potential gradient, and has it's origin in ionization produced by radioactive substances in the earth, close to the surface. In disturbed conditions, heavy rain is found to generate a negative space charge of the order of -1000µµC/m(^3) arising from a splashing effect at the earth's surface. In snowfalls charges of +500µµC/m(^3) originate from the charge on the Individual snowflakes and a positive charge left in the air due to rubbing or shattering of the snow as it is falling*The fait weather results in the first metro show a good agreement with those of Norinder, but higher up show the usual positive charge found by Kahler, Daunderer, Scrase, Obolensky and Brown.