Electric Fields and Conductivity Measured in the Stratosphere above Thunderstorms: Implications for the Global Electrical Circuit
The global electrical circuit, which maintains a potential of 280 kV between the earth and the ionosphere, is thought to be driven mainly by thunderstorms and ightning. However, very few in situ measurements of electrical current above thunderstorms have been successfully obtained. In this paper, we present dc to very low frequency electric fields and atmospheric conductivity measured in the stratosphere (30-35 km altitude) above active thunderstorms during the Sprite Balloon Campaign in southeastern Brazil (December 6-7, 2002). From these electric field and conductivity measurements, we calculate the conduction current density above the thunderstorms. We estimate the mean quasi-static conduction current during this period to be 2.5 A. Integration over the one hour duration of the easurements suggests that a total charge of 9000 C,about 2％ of the total net charge in the fair-weather atmosphere, is transferred from the thundercloud to the middle and upper atmosphere above the balloon altitude. We examine the transient conduction currents following a large (~500 C-km charge moment change) positive cloud-to-ground (+CG) lightning flash and a few typical –CG flashes. We find that the +CG flash transferred about -15 C of charge from the thundercloud to altitudes above the balloon, which acted to discharge the global circuit. Whereas, the typical –CG flash transferred only a few coulombs of charge to altitudes above the balloon and thus acted to weakly charge the global circuit. Hence, this case study suggests that quasi-static thundercloud charge, not lightning, is the primary driving mechanism for the global electrical circuit.
Jeremy N. Thomas Robert H. Holzworth Michael P. McCarthy
Dept.of Earth and Space Sciences, University of Washington, Seattle, WA, USA;National Geomagnetism P Dept.of Earth and Space Sciences, University of Washington, Seattle, WA, USA
国际会议
第13届国际大气电学会议(The 13th International Conference on Atmospheric Electricity)
北京
英文
2007-08-13（万方平台首次上网日期，不代表论文的发表时间）