Comparative measurements of the atmospheric electric space charge density made with the filtration and Faraday cage techniques

Close-to-ground measurements of the atmospheric space charge density simultaneously made with the direct filtration and Faraday cage techniques are reported. The data obtained on fair-weather days show that the measured values from the two techniques are small and agree with each other within the limits of experimental error during windy and turbulent conditions in the afternoon hours, but are large and vastly different, both in magnitude and polarity, during the calm and stable conditions at nighttime. The disagreement between the data obtained from the two techniques is explained due to the nonfulfillment of the requirement of maintenance of the entire Faraday cage in a region of uniform space charge density. It is concluded that the selection of a measuring technique for space charge in a study should be based on the requirements of the problem to be studied.