The electrical space charge in the lower atmosphere"

Abstract

Two space charge collectors were designed and built incorporating a glass-asbestos medium for filtering ions from the air, the charge being measured using a vibrating reed electrometer. These collectors were rigorously tested and it was demonstrated that they collected over 99.8% of the small ions in the air at certain flow rates through the collector. An analogue-to-digital converter was built in order to digitalise the information displayed on a 16 point recorder. The unit was built incorporating semiconductors; a voltage from the recorder was converted into a frequency which was counted on decatron tubes for a certain period of time, so that the number registered was within 1% of the recorded value. This number was then punched out on paper tape and arrangements were made in order to print 'space' and 'carriage return-line feed' into the output, Four aspirated psychrometers incorporating thermistors were built in order to measure the temperature and humidity gradients on a 21 m steel lattice mast. Wind was recorded at 1 m and 17 m and potential gradient in the surface of the earth and at the top of the mast. Results of space charge concentrations on the mast structure show that during a period of melting snow a charge separation occurs at the ground surface under strong wind conditions. It was also shown that dry blowing snow gives rise to high positive space charge even when the snow is blowing from distant hills. Corona space charge was observed to form at trees after a nearby lightning flash and during misty conditions there was a predominance of negative space charge. Convection cells were apparently detected under cumulus clouds and it was observed that charge was transported by the air circulations within these cells. Perhaps the most important result observed was an electrode effect due to the mast structure towards the top. This effect could completely mask the space charge density expected at that level if the mast were not there.