If you thought the exterior of the sun was hot, check out its corona. Although our star’s visible surface is less than 6000°C, its atmosphere blazes at up to 4 million°C.
Now, thanks to a telescope briefly boosted high above Earth by a small rocket, astronomers have found evidence of long-theorized magnetic processes that could help explain these blistering temperatures.
One reason the sun’s corona is so much hotter than its surface is comes down to a phenomenon known as wave heating, in which sound waves originating at the surface travel up through the corona.
There, friction among the particles boosts the temperature, says Jonathan Cirtain, a solar physicist at NASA’s Marshall Space Flight Center in Huntsville, Alabama. But wave heating provides only enough energy to heat the corona to about 1.5 million°C, he notes. And although most solar physicists agree that interactions among the sun’s magnetic field lines play a role in heating the corona, those processes haven’t been observed directly.
Now, Cirtain and his colleagues have gathered strong evidence to support the notion of a different kind of heating: magnetic heating. The team’s 3.2-meter-long, 210-kilogram camera-and-telescope combo rode a rocket into space above southern New Mexico on 11 July last year, observing the sun in a narrow band of extreme ultraviolet wavelengths that is normally blocked by Earth’s atmosphere.
The researchers targeted that band because one particular type of atom emits radiation in that range—an iron atom in which 11 of its normal complement of 26 electrons have been stripped away, also known as Fe XII. Although those highly charged ions exist most often at a temperature of about 1.5 million°C, data simultaneously gathered from other Earth-orbiting instruments provide information about material at even higher temperatures, Cirtain says.
Read More: Here