Magazine article Science News

Mapping Stormy Weather in the Ionosphere

Magazine article Science News

Mapping Stormy Weather in the Ionosphere

Article excerpt

Solar outbursts can roil Earth's ionosphere, rapidly changing the distribution of electric charge at high altitudes. In turn, these disturbances can damage orbiting satellites, disrupt radio communications, and cause harmful surges in electric power lines.

Although researchers have long used radar to study storms and other features of the ionosphere, they have lacked the tools needed to monitor and map it on a regular basis. A recent experiment has now furnished important data that will help scientists develop and refine a novel technique for producing global "weather" maps of the ionosphere.

Known as radio tomography, the technique involves the reconstruction of the three-dimensional distribution of ionospheric electric charge from its effect on radio signals sent from orbiting navigation satellites to ground-based receivers. It requires the same kind of mathematics used in medical tomography to construct three-dimensional X-ray images of biological tissue.

"Radar systems are too costly to build and run to do long-term, global monitoring of the upper atmosphere," says John C. Foster of the MIT Haystack Observatory in Westford, Mass. Radio tomography offers a relatively inexpensive way of achieving such coverage.

To test the validity of ionospheric radio tomography, Foster, Vyatcheslav E. Kunitsyn of Moscow State University, Evgeny D. Tereshchenko of the Polar Geophysical Institute in Murmansk, Russia, and their coworkers set up a joint experiment to see how well tomographic reconstructions stack up against radar measurements. The project, called the Russian-American Tomography Experiment (RATE), also allowed them to compare rival mathematical schemes for constructing the images. …

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