What are sunspots?
Bob Lin explains Sunspots and their importance in Sun Science.
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What are Sunspots?
LIN: Okay, sunspots are concentrations of the magnetic field of the sun. The magnetic field, for some reason that we don't completely understand, tends to concentrate in these spots, and when you get a concentration of a magnetic field, then it keeps the sun from heating that region as well as it would otherwise. So the region doesn't get quite as hot, and then it looks dark against the surface. And so we're able to see these sunspots that maybe we wouldn't have seen centuries ago, and by watching these sunspots, you notice that every eleven years you get more sunspots. And so that was how the original solar maximum and minimum were defined.
Now, the magnetic field in these sunspots is thousands of times what the Earth's magnetic field is, and so it's extremely strong. And for reasons that we don't understand, when we get very strong magnetic fields at the sun, then these other phenomena, like these explosions or flares, and the increase in the amount of radiation in different wavelengths and different colors, like extreme ultraviolets and soft X-ray, all increase. So we get things getting much hotter around the regions where the sunspots are. It's believed that all of these effects have to do with the very strong magnetic fields of the sunspots.
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