Earth: Plasmasphere
Earth: Plasmasphere
Space PlasmasIntroduction
Within the geocoronal zone, a low-energy population of charged particles exists in what is called the plasmasphere. These particles, carrying about 100 electron-Volts of energy are not permanent residents, but appear to be ionospheric ions injected into the geomagnetic field at low altitude. The plasmasphere is a complex, ever-changing system controlled by electrical currents within the magnetosphere, which cause this region to fill up and unload particles over the course of hours or days. The outer boundary of the plasmasphere, called the plasmapause, can change its position drastically from 20,000 to 40,000 kilometers from the Earth over the course of a few days. Though mostly a night-side feature, powerful convection currents can also move plasmasphere particles around into the dayside of the Earth.
The plasmasphere images by the NASA IMAGE satellite showing many previously unknown details.
The plasmasphere images by the NASA IMAGE satellite showing many previously unknown details. (Source: NASA-GSFC)
For decades, space physicists have assumed that the plasmasphere rotates in synchrony with the Earth, as Earth's magnetic field pulls these charged particles along. In 2003, the NASA IMAGE satellite showed that, when no space weather 'storms' are in progress, the inner plasmasphere actually rotates at a rate that is 10% slower than Earth so that the particles require about 27-hours to complete a full trip around the Earth. Comparisons with the DMSP satellite's ion drift data for the same events show that this '10%' corotation lag also exists in the ionosphere where it is caused by a process called the "ionospheric disturbance dynamo". This co-rotation lag result by IMAGE has far-reaching implications for scientists who are attempting to understand, and construct models of an important process called magnetospheric convection. Until this surprising result, scientists had always assumed strict co-rotation of the plasmasphere.
References
Notes
Imager for Magnetopause-to-Aurora Global Exploration (IMAGE) is the first satellite mission dedicated to imaging the Earth's magnetosphere, the region of space controlled by the Earth's magnetic field and containing extremely tenuous plasmas of both solar and terrestrial origin. Invisible to standard astronomical observing techniques, these populations of ions and electrons have traditionally been studied by means of localized measurements with charged particle detectors, magnetometers, and electric field instruments. Instead of such in-situ measurements, IMAGE employs a variety of imaging techniques to "see the invisible" and to produce the first comprehensive global images of the plasma populations in the inner magnetosphere. With these images, space scientists are able to observe, in a way never before possible, the large-scale dynamics of the magnetosphere and the interactions among its constituent plasma populations. (IMAGE - Southwest Research Institute)
Related EoC Articles
External Links
- IMAGE (Southwest Research Institute)
- IMAGE Education Center (NASA)
Preview Image
- The Earth’s plasmasphere (region of magnetosphere consisting of low energy plasma) as viewed by NASA’s IMAGE (Image for Magnetopause-to-Aurora Global Exploration) spacecraft. This view toward Earth’s north pole shows an emission from plasmaspheric helium ions appearing in false color as a pale green cloud surrounding the planet. (Source: NASA 50th Magazine: "50 Years of NASA Solar Exploration.")
Citation
Odenwald, Sten (Contributing Author); Bernard Haisch (Topic Editor). 2008. "Earth: Plasmasphere." In: Encyclopedia of the Cosmos. Eds. Bernard Haisch and Joakim F. Lindblom (Redwood City, CA: Digital Universe Foundation). [First published November 25, 2007].
<http://www.cosmosportal.org/articles/view/135526/>
Contact Us
Send to a Friend
Comments
There are no comments.