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The quaking ionosphere.

On April 12, 1978, something strange happened to the ionosphere above Chatanika, Alaska. Scientists routinely monitoring the flow of ionospheric particles detected very large verticle oscillations corresponding at times to ion velocities of up to 100 meters per second. Normally, ionospheric winds travel almost exclusively in the horizontal direction. And any verticle motions --rarely larger than 2 m/sec -- are usually associated with changes in the magnetic field, but no such variations were recorded that day.

The mystery was solved when Michael Kelley at Cornell University in Ithaca, N.Y., and Robert Livingston and Mary McCready at SRI International in Menlo Park, Calif., linked the nine-hour-long ionospheric disturbance to an earthquake that had occurred 1,000 kilometers from the radar site just before the oscillations began. As discussed in the September GEOPHYSICAL RESEARCH LETTERS, the researchers found that their data compared well with a theory developed 18 years ago, which predicts that a nuclear explosion or earthquake will excite atmospheric motion near the event much like that created when a pebble falls in water.

In order to fit the data to the model, however, they had to assume that the ionosphere was hotter than normal, suggesting that the earthquake had heated the upper atmosphere. According to Kelley, energy from earthquakes, tornadoes and weather in the lower atmosphere may play a much more important role in warming the upper atmosphere than has usually been assumed.
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Title Annotation:earthquake disturbs ionosphere
Publication:Science News
Date:Oct 19, 1985
Words:234
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