What is Solar Tsunami?

Washington, Aug 3, 2010: The Earth could be hit by a solar tsunami anytime, as an unusually complex magnetic eruption on the Sun has flung a large cloud of electrically charged particles towards earth, scientists have warned.

The explosion, called a coronal mass ejection, was aimed directly towards Earth, which then sent a "solar tsunami" racing 93 million miles across space, the New Scientist reported.

Astronomers from all over the world witnessed the huge flare above a giant sunspot the size of the Earth, which they linked to an even larger eruption across the surface of Sun.

Experts said the wave of supercharged gas will likely reach the Earth on Tuesday, Aug 3, when it will buffet the natural magnetic shield protecting Earth.

Several satellites, including Nasa's new Solar Dynamics Observatory, recorded on Sunday, Aug 1, a small solar flare erupting above sunspot 1092, the size of the Earth.

The satellites also recorded a large filament of cool gas stretching across the Sun's northern hemisphere also exploded into space.

"This eruption is directed right at us," said Leon Golub, of the Harvard-Smithsonian Centre for Astrophysics.

However, a really big solar eruption could even shut down global communication grids and destroy satellites also

Source:  http://news.oneindia.in/2010/08/03/solar-tsunami-from-sun-may-hit-earth.html

A Moreton wave is the chromospheric signature of a large-scale solar coronal shock wave. Described as a kind of solar'tsunami',^[1] they are generated by solar flares. They are named for American astronomer Gail Moreton, an observer at the Lockheed Solar Observatory in Burbank who spotted them in 1959. ^[2][3][4][5] He discovered them in time-lapse photography of the chromosphere in the light of the Balmer alpha transition.

There were few follow-up studies for decades. Then the 1995 launch of the Solar and Heliospheric Observatory led to observation of coronal waves, which cause Moreton waves. Moreton waves were a research topic again. (SOHO's EITinstrument discovered another, different wave type called 'EIT waves'.)^[6] The reality of Moreton waves (aka fast-modeMHD waves) has also been confirmed by the two STEREO spacecraft. They observed a 100,000-km high wave of hot plasma and magnetism, moving at at 250 km/second, in conjunction with a big coronal mass ejection in February 2009.^[7][8]

Moreton waves propagate at a speed of 500-1500 km/s, and occur where a coronal magnetohydrodynamic fast-mode weak shock wave intersects the chromosphere according to a well-known theory of Yutaka Uchida that links them to radio type II bursts. Moreton waves can be observed primarily in the Hα band.^[9]

^{Source:  http://en.wikipedia.org/wiki/Moreton_wave}

3-D Solar Tsunami Video Shows the Extreme Waves Are Real

A 60,000-mile-high wave of super-hot plasma blazing across the sun’s surface at 560,000 mph? Yep.
“Now we know. Solar tsunamis are real,” said John Gurman of the Solar Physics Lab at the Goddard Space Flight Center, in a press release Tuesday.
NASA’s Solar Terrestrial Relations Observatory has confirmed that the crazy circular bursts on the surface of the sun, rising higher than the Earth is wide, aren’t just optical illusions.
STEREO consists of two spacecraft pointing at the sun, one ahead of Earth in its orbit and one behind, that acquire stereoscopic images of the sun to give a sort of three-dimensional view, similar to the way our two eyes do.
Though these solar tsunamis, technically known as fast-mode magnetohydrodynamical waves, were first seen by the SOHO mission more than a decade ago, the single spacecraft couldn’t determine if the wave was real or the shadow of a coronal mass ejection. But in February the STEREO twins were perfectly poised to catch the eruption of a sunspot that spawned a wave, seen in the movie above.
“It was definitely a wave,” George Mason University scientist Spiros Patsourakos, lead author of a paper on the solar tsunamis in August in The Astrophysical Research Journal Letters, said in a press release. “Not a wave of water,” he adds, “but a giant wave of hot plasma and magnetism.”



The spacecraft have also spotted waves crashing into other solar structures.
“We’ve seen the waves reflected by coronal holes. And there is a wonderful movie (at right) of a solar prominence oscillating after it gets hit by a wave (near the top of the image),” co-author Angelos Vourdilas of the Naval Research Lab in Washington, D.C., said in a press release. “We call it a dancing prominence.”
Watching the waves interact with other things can reveal new information about the sun’s atmosphere, and help forecast when a coronal mass ejection or radiation storm will impact Earth.
Movies: NASA
NASA press release
Citation: “‘Extreme Ultraviolet Waves’ are Waves: First Quadrature Observations of an Extreme Ultraviolet Wave from STEREO.” by Spiros Patsourakos and Angelos Vourlidas, Astrophysical Research Journal Letters, vol. 700, August 1, 2009.


Source:  By Betsy Mason   http://www.wired.com/wiredscience/2009/11/solar-tsunami/