We've studied sunspots for over 400 years but have never been able to reliably predict their appearances. That is, until three Stanford researchers developed a technique to find them days before they hit the Photosphere.

Sunspots—planet-sized islands of magnetism in the solar plasma—appear as black spots on the solar disc and are visible with the naked eye. They're often precursors to Coronal Mass Ejections (CME) and solar flares, phenomena that wreak havoc on Earthly electronics and the Aurora Borealis alike. The problem is that, up until now, sunspots were only visible when they reached the surface—leaving precious little time before the CME itself occurs and no means of knowing if it would actually strike the planet.

However, PhD student Stathis Ilonidis and her colleagues Junwei Zhao and Alexander Kosovichev have come up with a solution—a technique known as "time-distance helioseismology." It measures the acoustic waves that travel through the sun to "see" spots 60,000km below the solar surface, much in the same way that seismologists employ seismic waves to observe actions deep below Earth's crust.

"There are limits to the technique," Ilonidis said. "We can say that a big sunspot is coming, but we cannot yet predict if a particular sunspot will produce an Earth-directed flare." The team hopes to eventually refine their prediction algorithm and lengthen our advanced warning of solar activity from hours to days.


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