National Academies Press: OpenBook

The Earth's Electrical Environment (1986)

Chapter: 15 The Global Atmospheric-Electrical Circuit

« Previous: References
Suggested Citation:"15 The Global Atmospheric-Electrical Circuit ." National Research Council. 1986. The Earth's Electrical Environment. Washington, DC: The National Academies Press. doi: 10.17226/898.
×
Page 206

Below is the uncorrected machine-read text of this chapter, intended to provide our own search engines and external engines with highly rich, chapter-representative searchable text of each book. Because it is UNCORRECTED material, please consider the following text as a useful but insufficient proxy for the authoritative book pages.

THE GLOBAL ATMOSPHERIC-ELECTRICAL CIRCUIT 206 15 The Global Atmospheric-Electrical Circuit Raymond G. Roble and Israel Tzur National Center for Atmospheric Research Lightning was recognized as a grand manifestation of static electricity within thunderstorm clouds in the eighteenth century. It was also recognized that electrical phenomena are not confined to thunderclouds and that a weak electrification exists as a permanent property of the atmosphere even during fair weather. Further research established that the Earth's surface is charged negatively and the air is charged positively, with a vertical electric field of about 100 V/m existing in the atmosphere near the Earth's surface. An electrostatic explanation for the phenomena was sought at first, and one theory suggested that the electric field of the atmosphere was the result of an intrinsic negative charge on the Earth, probably collected during the Earth's formation. With the discovery of cosmic-ray ionization in the early twentieth century, it was realized that air possesses an electrical conductivity due to its ion content. As a result of the finite electrical conductivity, vertical conduction currents flow from the atmosphere to the Earth, tending to neutralize the charge on the Earth. On the basis of actual conductivity values it was calculated that charge neutralization would take place in less than an hour, and the continued existence of an electric field suggested some generation mechanism to oppose the leakage currents flowing to the Earth. The search for this generation mechanism soon became the main object of research on global atmospheric electricity. In the early twentieth century the concept of a global circuit of atmospheric electricity slowly began to evolve (Israël, 1973; Pierce, 1977). The net positive space charge in the air between the ground and a height of about 10 km is nearly equal to the negative charge on the surface of the Earth. The electrical conductivity of the air increases rapidly with altitude, and the product of the local vertical electric field and local conductivity at any altitude within an atmospheric column gives a constant air-earth current flowing downward. This constant air-earth current with respect to altitude implies that the current flow is mainly driven by a constant difference in potential between the surface of the Earth and some higher altitude in the atmosphere. The discovery of the highly conducting ionosphere in the 1920s explained the long-range propagation of radio waves and was important for the evolution of the concept of the global electric circuit. The ionosphere, with its large electrical conductivity, provided a means of closing the global circuit. It, however, is not a perfect conductor parallel to the Earth's surface, but it possesses a finite conductivity, and the electric currents and fields within it are driven by the combined action of the ionospheric and magnetospheric dynamo systems as well as by current generation from the lower atmosphere. Wilson (1920) first demonstrated that a thunderstorm supplies a negative charge to the Earth. In the 1920s, it was also known that over the oceans and in polar areas

Next: THUNDERSTORMS AS GENERATORS IN THE GLOBAL CIRCUIT »
The Earth's Electrical Environment Get This Book
×
Buy Paperback | $75.00
MyNAP members save 10% online.
Login or Register to save!
Download Free PDF

This latest addition to the Studies in Geophysics series explores in scientific detail the phenomenon of lightning, cloud, and thunderstorm electricity, and global and regional electrical processes. Consisting of 16 papers by outstanding experts in a number of fields, this volume compiles and reviews many recent advances in such research areas as meteorology, chemistry, electrical engineering, and physics and projects how new knowledge could be applied to benefit mankind.

  1. ×

    Welcome to OpenBook!

    You're looking at OpenBook, NAP.edu's online reading room since 1999. Based on feedback from you, our users, we've made some improvements that make it easier than ever to read thousands of publications on our website.

    Do you want to take a quick tour of the OpenBook's features?

    No Thanks Take a Tour »
  2. ×

    Show this book's table of contents, where you can jump to any chapter by name.

    « Back Next »
  3. ×

    ...or use these buttons to go back to the previous chapter or skip to the next one.

    « Back Next »
  4. ×

    Jump up to the previous page or down to the next one. Also, you can type in a page number and press Enter to go directly to that page in the book.

    « Back Next »
  5. ×

    To search the entire text of this book, type in your search term here and press Enter.

    « Back Next »
  6. ×

    Share a link to this book page on your preferred social network or via email.

    « Back Next »
  7. ×

    View our suggested citation for this chapter.

    « Back Next »
  8. ×

    Ready to take your reading offline? Click here to buy this book in print or download it as a free PDF, if available.

    « Back Next »
Stay Connected!