AIRBORNE ATMOSPHERIC ELECTRIC MEASUREMENTS OVER A MOUNTAIN RIDGE AND IN RADIOACTIVE DEBRIS

Abstract

The atmospheric conductivity and potential gradient were measured from an airplane over the Blue Ridge in Virginia on 2 March 1955, before the arrival of radioactive debris from a burst in Nevada the preceding day. Above the exchange layer top at 9000 ft, the conductivity approached that of clean air, particularly over the foothills downwind of the ridge. The vertical conduction-current density directly over the ridge was some 1.5 times that over the adjacent lowlands, due to convergence of the electric lines of force. On 3 March, at 20,000 ft, the research airplane encountered the debris over southern Virginia, where the maximum total measured conductivity was 43.2 ? 10?14 mho-m?1. This is 1.6 times the corresponding value measured on 2 March, and 1.4 times the highest conductivity obtained at this altitude during a total of 28 soundings over a wide area. Application of the ionization-equilibrium equation with the assumption of zero large ion density yields an increase in ionizing radiation at the point of maximum conductivity to at least 2.5 times the cosmic-ray background. The conduction-current density within the radioactive debris was substantially the same as that outside the debris, causing the potential gradient to vary approximately as the reciprocal of the conductivity. Because of its stability above the exchange layer, the conductivity is a useful as well as a sensitive indicator of such radioactive debris. Neither the potential gradient nor the current density is suitable for this purpose, because of the larger normal ranges of variation.