X-ray picture of

Discussion of Solar Image

The solar picture you just saw is an X-ray image, like the one above. That is, it was made by focusing the X-rays that are produced by the Sun's hot outer atmosphere. X-rays are produced where the temperature of the superhot gas (or "plasma") reaches more than a million degrees, and where the density of the plasma exceeds a certain threshold. Since X-rays are invisible, we have digitized the images and made them false-color so you can see where the hottest, most dense, plasma is located. The electrically charged (that is, not neutral) plasma is tied to the magnetic field, so the brighter condensations in the image are "active regions" where the magnetic field is concentrated.

NOTE: It's only been about fifty years that we've known that the Sun even produces X-rays. Why the outermost atmosphere of the Sun (called the "corona") is hot enough to do this is still a mystery.