The Sun’s atmosphere, or corona, is spectacularly hot—far, far hotter than the Sun’s surface. Why this is is still something of a mystery, and scientists watching the Sun’s surface have built software that looks at the heating and cooling occurring in the corona in an attempt to understand how fast temperature changes happen.
Above is an ultraviolet image of a small patch of the sun’s corona. The right half has been processed with a computer program so sections that are growing cooler over a 12-hour period are colored yellow, orange, and red, while heating sections are labeled blue and green.
Nicholeen Viall, the NASA solar scientist who developed the program, found that most of the temperature changes she saw over that period were cooling, which suggests that heating in the corona is probably happening very quickly, so quickly that it doesn’t show up over an observation period of this length. This lends credence to the idea that the corona is heating up in short bursts, rather than continually.
You can watch how the image was made in the video below: