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Wednesday, June 18, 2008

Giant Solar Tsunami Viewed from NASA's STERO Spacecraft

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Just as earthquakes can set off huge tsunami waves on the surface of our oceans, a coronal mass ejection or flare can cause a tsunami on the Sun's surface—and it did on May 19, 2007. The waves generated by the explosions can travel at over a million kilometers per hour. The event was captured by NASA's twin Stereo spacecraft and was observed by a team at Trinity College, Dublin.

The event lasted for about 35 minutes and ultimately covered almost the full disk of the Sun. “The energy released in these explosions is phenomenal, about two billion times the annual world energy consumption in just a fraction of a second,” stated Long.

A previous observation of a solar tsunami was recorded by the SOHO spacecraft almost a decade ago but these images were misleading to scientists. Theorists were unable to match the anticipated behaviors of the tsunami to the observation because theory suggested that the solar tsunamis would travel much faster that observed. According to their calculations, tsunamis on the Sun should have had phenomenal speed due to the influence of the Sun's magnetic field on the solar material—making the waves magneto-acoustical in nature. With the improved capabilities of the Stereo's Extreme Ultraviolent Imager (EUVI) instruments they in fact measured speeds in agreement with the theory. In addition, by monitoring the Sun at four wavelengths which penetrate different layers of the Sun's atmosphere, astronomers could see how the wave moved vertically as well as horizontally.

“We were able to show for the first time that this wave actually propagates almost all the way from the surface of the Sun to high up in the Sun's atmosphere,” said Dr. Gallagher, a colleague of Long.

The researchers even saw the pressure wave reflect and refract off different regions of the Sun's atmosphere exactly as Earth's tsunami's do as they crash against land. This past April it was reported at the RAS National Astronomy Meeting by David Long.

Posted by Dr. Chandra Walker

Original here

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