(via Scientists see sunspots forming 60,000 km below the Sun’s surface! | Bad Astronomy | Discover Magazine)
Using sound waves, scientist manning the two big NASA solar observatories, SOHO and SDO, have been able to see 60,000 km beneath the surface of the sun to catch a sunspot forming 2 days before we see it as an actual sunspot.
Here’s Phil’s explanation:
Basically, inside the Sun, hot plasma (gas stripped of one or more electrons) rises and cooler plasma sinks. As it moves, it generates turbulence. This in turn creates acoustic waves — sounds — that travel through the Sun. As these waves move through the solar interior, regions with different densities make them speed up or slow down. The physics of this is pretty well understood, so by mapping how long it takes a wave to move between two points, the density of the stuff between them can be measured.
And to do this, they collect a seriously insane amount of data from those two observatories. Billions of data points. They’ve got some pretty damn good algorithms for filtering the noise, and are increasing how much forewarning they can give of new sunspots. Very useful considering that the subatomic particles flying at a good fraction of the speed of light that a solar flare or coronal mass ejection can throw off are dangerous to satellites, the ISS, and even our power grid down here.