ARLA/CLUSTER: Detectar Manchas Solares antes delas serem visiveis.

[João Gonçalves Costa]

New breakthrough in sunspot prediction

A PhD student at Stanford University, Stathis Ilonidis, has found a way to detect sunspots before they are visible to the human eye. His findings could lead to significant advances in space weather forecasting.

Sunspots are the "butterfly's wings" of solar storms. Visible to the human eye as dark blemishes on the solar disk, sunspots are the starting points of explosive flares and coronal mass ejections (CMEs) that sometimes hit our planet 150 million kilometers away.

Astronomers have been studying sunspots for more than 400 years, and they have pieced together their basic characteristics: Sunspots are planet-sized islands of magnetism that float in solar plasma. Although the details are still debated, researchers generally agree that sunspots are born deep inside the sun via the action of the sun's inner magnetic dynamo. From there they bob to the top, carried upward by magnetic buoyancy; a sunspot emerging at the stellar surface is a bit like a submarine emerging from the ocean depths.

The analysis technique is called "time-distance helioseismology" It is similar to an approach widely used in earthquake studies. Just as seismic waves traveling through the body of Earth reveal what is inside the planet, acoustic waves traveling through the body of the sun can reveal what is inside the star.

Submerged sunspots have a detectable effect on the sun's inner acoustics-namely, sound waves travel faster through a sunspot than through the surrounding plasma. A big sunspot can leapfrog an acoustic wave by 12 to 16 seconds. By measuring these time differences, researchers can find the hidden sunspot.

There are limits to the technique, it is possible to forecast that a big sunspot is coming, but if a particular sunspot will produce an Earth-directed flare can not be predicted.

So far they have detected five emerging sunspots - four with SOHO and one with SDO. Of those five, two went on to produce X-class flares, the most powerful kind of solar explosion. This encourages the team to believe their technique can make a positive contribution to space weather forecasting.

Fonte: SARL
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