Stratospheric Electricity

The motivation behind the study described in this report is the possible climatic impact of operating a fleet of supersonic transports (SSTs). The report first summarizes information on the physical properties of the stratosphere and on its gaseous and particulate trace consituents. A critical review of experimental data on stratosphere electrification is then presented. Information is given on profiles of conductivity (positive and negative); small- (cluster-) ion densities (positive and negative); and electric field. Some of the experimental results are shown to be suspect. The more reliable experimental results, obtained between 10 and 30 km, indicate conductivities increasing monotonically with increasing height; electric fields decreasing monotonically as height increases; small-ion densities of the order of thousands per cu cm with a maximum at about 15 km; little space charge; a constant vertical air/earth current; and positive and negative small-ion mobilities. Fine- and larger-scale spatial and temporal variations are superimposed upon the general trend of the results. Simple theory shows that the major phenomena of stratospheric electricity can be mostly explained by considering ion production by cosmic rays alone, and ion loss only by mutual neutralization (recombination). It was concluded that stratospheric electrification is little affected by gaseous constituents, but should be quite responsive to changes in the number density and size distribution of the stratospheric aerosol. (Modified author abstract)