Just in time for our physics test — on electromagnetism — the Sun has had a Coronal Mass Ejection of charged particles that is heading toward the Earth.
[The Coronal Mass Ejection] is moving at almost 1,400 miles per second, and could reach Earth’s magnetosphere – the magnetic envelope that surrounds Earth — as early as tomorrow, Jan 24 at 9 AM ET (plus or minus 7 hours). This has the potential to provide good auroral displays, possibly at lower latitudes than normal.
— Fox, 2012: M8.7 Solar Flare and Earth Directed CME from NASA.
A Coronal Mass Ejection has about 100 billion tons of electrons, protons and other particles (NASA Cosmicopia, 2011), usually ionized, that would bombard the Earth and the atmosphere if we weren’t protected by the Earth’s magnetic field.
Most of the ions are deflected around the Earth but some get focused down toward the poles. At the poles, these ions hit nitrogen and oxygen molecules (that make up 98% of the atmosphere), exciting many of them. Excited atoms and molecules give off light. The light shows created are called the auroras.
I like the second video they post because, at the end, there is a splatter of interference from all the charged particles affecting the detector.