These nanoflares, as astronomers dubbed them, could pay the solar coronal heating bill, assuming there were enough of them. These aren’t the source of coronal heating-flares don’t happen very often-but what if big ones are only (so to speak) the tip of the iceberg? What if there are little ones, lots of them, too small to see? These are storms of ridiculous power a single flare can explode with as much power as 10 billion one megaton H-bombs. These store unbelievable amounts of energy and when they twist up and tangle, they can snap, releasing that energy as solar flares. The Sun has a complex magnetic field, caused by its internal motion, which can generate huge, towering loops above the photosphere. There’s not much on the large scale that seems to show why the corona should be so hot.īut there are hints. The Sun is more than 100 times wider than Earth, 1.4 million kilometers across, and the corona even larger.
It’s also so hot it glows at wavelengths of light that don’t penetrate our atmosphere like far ultraviolet and X-rays, so we need space-based observatories to study it (usually hang on for the important exception).Īlso, the scale is a tad mind-crushing. Observing the corona is difficult the plasma there is incredibly thin and faint. Inside the Sun, the temperature drops as you move out from the center, but that trend reverses, viciously, at the corona.Īstronomers have tried to explain this for years, coming up with lots of mechanisms. The thing is, while the photosphere is hot, roughly 5,500° C, the corona is freaking hot, 2 million degrees on average. Above this layer is the corona, what you can think of as the Sun’s atmosphere: extremely thin gas. The layer we see is called the photosphere (“sphere of light”), because that’s where the material in the Sun gets thin enough that light can easily fly out. It doesn’t really have a surface, instead just sort of fading away with height. The Sun is a huge ball of plasma, * gas so hot that electrons are ripped from their parent atoms. This week, astronomers announced they have found the smoking gun. The Sun’s atmosphere-its corona-is far, far hotter than its surface, and this has been a long-standing mystery, baffling astronomers for decades.
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