HMI4096 / by Jason Mann

This image is today's image of the Sun from the HMI instrument aboard the Solar Dynamics Observatory. Look at the full image, and zoom in on one of the sunspots. The dark part of a spot is the umbra, the less-dark area is called the penumbra. The umbra has the strongest and most homogeneous magnetic field; pretty much 3000G +/- 500, and pretty much going directly outward from the "solar surface". The penumbra, on the other hand, is made up of fine strands, some very inclined and lying close to the solar surface, some less inclined and heading up into the corona; some stronger and some weaker, but generally around 1000G. The structure in the penumbra has been likened to two combs (like for your hair) shoved together with some tines going horizontally, the others going vertically, in between each other.