sunspot AR2736
Two days ago, sunspot AR2736 didn't exist. Now the rapidly-growing active region (movie) stretches across more than 100,000 km of the solar surface and contains multiple dark cores larger than Earth. Moreover, it has a complicated magnetic field that is crackling with C-class solar flares. The sunspot is inset in this magnetic map of the sun from NASA's Solar Dynamics Observatory:

The rapidly-growing sunspot AR2736
© NASA
The rapidly-growing sunspot AR2736.

Sunspots are islands of magnetism floating on the surface of the sun. Most sunspots, like most magnets, have two poles + (N) and - (S). Sunspot AR2736, however, has multiple poles with areas of + and - jostling against one another. This is why the sunspot is crackling with flares. Magnetic field lines of opposing polarity criss-cross and explode--a process known as magnetic reconnection.

In the grand scheme of space weather, C-class solar flares are not considered to be major events. However, these explosions are noteworthy now because the sun has recently been so quiet. Solar Minimum is underway. In context, C-flares represent a real uptick in solar activity. They can ionize the top of Earth's atmosphere, disturb shortwave radio communications, and even hurl CMEs toward Earth. Indeed, one is heading our way now. Stay tuned.