STUDIES OF AN ARTIFICIALLY GENERATED ELECTRODE EFFECT AT GROUND-LEVEL

The outdoor experiments, using a metallic grid above the ground surfac e, have yielded well-defined vertical profiles of the space-charge den sity. The profiles showed strong evidence for the existence of an elec trode effect, which could be named the artificial electrode effect and can serve as a very useful and well-controlled model for the study of atmospheric electric processes in the atmospheric surface layer. The build-up or break-down of an electrode-effect layer occurred in a time of the order of 10 s under the experimental conditions realized. The artificially generated electrode effect is dependent on the electrical field strength supplied, wind speed, turbulent mixing and ion mobilit ies. Wind speed and ion mobility seem to be the dominant factors, defi ning space-charge density profiles. A theoretical model for the artifi cial electrode effect has been developed, taking into account turbulen t mixing of charged particles in the air flow with the logarithmic pro file of the wind velocity. The numerical analysis of the boundary valu e problem for the two-dimensional equations for the light ion concentr ations has been performed. The model presented shows a qualitative agr eement of calculated space-charge profiles with measured ones, and exp lains the dependence of the artificial electrode effect on the dominan t control parameters. The limiting conditions for the developed theory are discussed.