National Academies Press: OpenBook

The Earth's Electrical Environment (1986)

Chapter: 14 Upper-Atmosphere Electric-Field Sources

« Previous: References
Suggested Citation:"14 Upper-Atmosphere Electric-Field Sources ." National Research Council. 1986. The Earth's Electrical Environment. Washington, DC: The National Academies Press. doi: 10.17226/898.
Page 195

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.

UPPER-ATMOSPHERE ELECTRIC-FIELD SOURCES 195 14 Upper-Atmosphere Electric-Field Sources Arthur D. Richmond National Center for Atmospheric Research The Earth's space environment is filled with electrons and positive ions, comprising a plasma of very low density. These charged particles collide only infrequently and are strongly influenced by magnetic and electric fields. In turn, the charged particles affect the distributions of the magnetic and electric fields in space. The space plasma environment, therefore, is dominated by electrodynamic processes. The regions of space involved in creating upper atmosphere electric fields are illustrated in Figure 14.1 and are described below. The solar wind is a plasma with electron and ion number densities of order 5 × 106 m–3 flowing continually outward from the Sun at a speed of 300-1000 km/sec. Imbedded within it is the interplanetary magnetic field (IMF), which is maintained by electric currents flowing throughout the solar-wind plasma. The IMF strength at the orbit of the Earth is roughly a factor of 10–4 smaller than the strength of the surface geomagnetic field. Most of the time, an interplanetary field line near the Earth can be traced back to the surface of the Sun, where magnetic fields are ubiquitous. As the Sun rotates (once every 27 days) different magnetic regions influence the IMF near the Earth. The combination of solar-rotation and outward solar-wind flow produce a roughly spiral IMF pattern. In addition, the solar- wind velocity can change dramatically and produce both large-scale and small-scale distortions of the IMF so that the field direction and strength vary greatly. These changes have been found to influence the electrical state of the magnetosphere and ionosphere. The magnetosphere is the region of space where the geomagnetic field has a dominant influence on plasma properties. As the charged particles of the solar wind are deflected by the geomagnetic field, an electric current layer is formed at the boundary between the solar wind and the magnetosphere, called the magnetopause. This current layer distorts the geomagnetic field from the dipole-like configuration that it would otherwise have and helps to create a long magnetized tail trailing the Earth. Although the full extent of this tail has not yet been determined, it is known to be more than 500 Earth radii. The magnetosphere contains the radiation belt, composed of energetic charged particles trapped in the magnetic field. The number density of electron-ion pairs in the magnetosphere is highly variable, ranging in order of magnitude from a low of 106 m–3 in parts of the tail up to 1012 m–3 in the densest portions of the dayside ionosphere. The ionosphere is the ionized component of the Earth's upper atmosphere. It is not distinct from the magnetosphere, but rather forms the base of the magnetosphere in terms of electrodynamic processes. The lower boundary of the ionosphere is not well defined but can be taken as about 90 km altitude for the present pur

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,'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!