Earth's magnetic field has been strongly disturbed since Monday morning, creating a geomagnetic storm seen in parts of the world.
This is a time-lapse video of a geomagnetic storm seen over Denmark.
A coronal mass ejection, or CME, caused it. That CME compressed the magnetosphere and ignited auroras.
To put that in more understandable terms, a geomagnetic storm is basically an interaction with the Earth's magnetic field.