Nov. 20 - Mystery of the Solar Tsunami -- Solved (w/ Video)

Dear Friends,

Click the link if you can't access the video/don't receive the images.

http://www.physorg.com/news177872248.html

Love and Light.

David

Mystery of the Solar Tsunami -- Solved (w/ Video)

November 19, 2009

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The unique orbit of STEREO's twin spacecraft allowed scientists to confirm the existence of solar tsunamis. Credit: NASA

(PhysOrg.com) -- Sometimes you really can believe your eyes. That's what NASA's Solar Terrestrial Relations Observatory (STEREO) is telling researchers about a controversial phenomenon on the sun known as the "solar tsunami."

Years ago, when solar physicists first witnessed a towering wave of hot plasma racing across the sun's surface, they doubted their senses. The scale of the wave was staggering: It rose up higher than Earth itself and rippled out from a central point in a circular pattern millions of kilometers in circumference. Skeptical observers suggested it might be a shadow of some kind—a trick of the satellite's eye—but surely not a real wave.

"Now we know," says Joe Gurman of the Solar Physics Laboratory at NASA's Goddard Space Flight Center. "Solar tsunamis are real."

Violent events on the Sun can trigger waves much the same as earthquakes can trigger tsunamis on the Earth, as shown in this computer simulation. Credit: NASA/Walt Feimer, GSFC Conceptual Image Lab

The twin STEREO spacecraft confirmed their reality in February 2009 when sunspot 11012 unexpectedly erupted. The blast hurled a billion-ton cloud of gas (a coronal mass ejection, or CME) into space and sent a tsunami racing along the sun's surface. STEREO recorded the wave from two positions separated by 90 degrees, giving researchers an unprecedented view of the event.

"It was definitely a wave," says Spiros Patsourakos of George Mason University, lead author of a paper reporting the finding in Astrophysical Journal Letters. "Not a wave of water, but a giant wave of hot plasma and magnetism."

The technical name is "fast-mode magnetohydrodynamical wave," or "MHD wave" for short. The one STEREO saw reared up about 100,000 kilometers high, raced outward at 250 km/second (560,000 mph), and packed as much energy as 2400 megatons of TNT (1029 ergs).

Solar tsunamis were discovered in 1997 by the Solar and Heliospheric Observatory (SOHO). In May of that year, a CME came blasting up from an active region on the sun's surface, and SOHO recorded a tsunami rippling away from the blast site.

"We wondered," recalls Gurman, "is that a wave, or just a shadow of the CME overhead?"

SOHO's single point of view was not enough to answer the question—neither for that first wave nor for many similar events recorded by SOHO in years that followed.

The question remained open until after the launch of STEREO. At the time of the February 2009 eruption, STEREO-B was directly over the blast site, while STEREO-A was stationed at a right angle —"perfect geometry for cracking the mystery," says co-author Angelos Vourlidas of the Naval Research Laboratory in Washington, D.C.