An X-class flare just before a coronal mass ejection
A coronal mass ejection (CME) happens when a closed field in the outer solar atmosphere (also known as the corona) violently releases gas and magnetic fields into space. Anything that gets in the way of these CMEs is immediately cooked by a billion tons of matter moving several million miles per hour. CMEs are often associated with solar flares, but can happen on their own. When they reach our planet, we see them as auroras.
Pictured here is an X-class solar flare as observed by the Solar Dynamics Observatory on Nov. 3, 2011. NASA says radio transmissions were disrupted on Earth some 45 minutes after this flare. A few hours later, a CME burst off the backside of the sun, sending energy pouring in the direction of Venus.