Coronal Mass Ejections

The term "coronal mass ejection" (CME) relates to what happens every time the sun throws off a huge ball of plasma. Basically, the surface of the sun is riddled with powerful magnetic lines crisscrossing in an intricate, and very confusing, pattern. Super heated plasma from the sun will flow along these magnetic lines forming arcs large enough to allow several Earths to pass through. On occasion, these magnetic lines will come into contact with each other, or otherwise decide to reorder themselves, and when this happens there is a massive explosion that throws some of that super heated plasma into space. To put it into simpler terms, a CME is a burst of highly charged protons, electrons and some heavier particles that is thrown into space.

The powerful magnetic lines across the surface of the sun are very confusing. Source

Here a long standing magnetic filament explodes, releasing a CME. Source

On occasion these waves of charged particles will come into contact with a planet, at which point they become interplanetary CMEs (ICMEs). When this happens on the Earth, the planets own magnetic field acts like a shield and blocks out most of the powerful blast. Earth's magnetic field isn't a perfect shield, however. Powerful ICMEs can cause geomagnetic storms and will deform the magnetic field. When these ICMEs hit, the charged particles are directed along the magnetic field to the Earth's poles where they interact with the atmosphere, creating beautiful aurorae, one of the most notable being the aurora borealis (Northern Lights). 

Earth's magnetic field is distorted by CMEs. Source

Aurora. Source

Aurora borealis from space. Source

As we move into solar maximum, the high point of solar activity, CMEs will occur more frequently, and the aurorae will get brighter and more fascinating. CMEs can cause damage to electrical equipment if they are powerful enough, so some people worry that we are in danger considering that this solar maximum is supposed to be one of the most powerful to date, but in all likelihood, we'll just have some more pretty lights in the sky.

Now doesn't that just look badass? Source