Geoscience Reference
In-Depth Information
Chapter 3
Atmospheric Electricity
Abstract In this chapter the main attention is paid on the atmospheric electricity
and on the global lightning activity as a machine supplying the negative charges
to the Earth. Here we deal with the electric field and charge distribution in
thunderstorm clouds and with the conventional mechanism for air breakdown.
Lightning discharge parameters and global thunderstorm activity are discussed.
In the remainder of this chapter the main emphasis is on the low frequency effects
associated with recently documented evidences of previously unknown forms of
upward propagating gigantic electric discharges, also known as transient luminous
events (TLEs), which occur above a large thunderstorm system.
Keywords Global thunderstorm activity ￿ Lightning return stroke ￿ Runaway
electron breakdown ￿ Streamer ￿ Transient luminous events (TLEs)
3.1
Global Electric Circuit
3.1.1
Electric Field and Conductivity of the Atmosphere
It is usually the case that the clouds, precipitation, fogs, and dust clouds contain a
large amount of spatial electric charges. The electric field permanently exists in the
atmosphere even though there is a fine weather condition. Near the ground surface
the so-called fair weather electric field, i.e., the steady electric field, is vertically
downward with mean value of about 100-130 V/m. The solid Earth is negatively
charged with net charge about 3 10 5 C, while the positive charges are mainly con-
centrated in the lower atmosphere. Under fair weather conditions the atmospheric
electric field falls off with height as shown in Fig. 3.1 , so that its value is no more
than several volts per meter at the height about 10 km. Owing to the presence of
charged aerosols the electric field may increase in amplitude in the mixing layer over
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