On average how long do the auroras last?
The beautiful luminescence of the aurora is caused by streams of energetic electrons that become trapped on Earth’s magnetic field lines and spiral along them until the magnetic lines dip into Earth’s atmosphere near the poles. In these regions around, but not at, the poles, the electrons collide with atmospheric atoms which become excited and give off colored light characteristic of the atom and how excited it is. When the electron stream cuts off, the auroral glow immediately fades as well. These energetic electrons come from the Sun but don’t flow directly into the auroral ovals. Instead, they first gain entry into Earth’s magnetosphere, probably slide into the magnetotail (a long extension of the magnetosphere on the dark side of the Earth) where they are temporarily stored. Then, when the magnetosphere becomes unstable with too much stored energy or a disturbance from the soalr wind, there is a sudden release of the stored electrons and a consequent auroral glow. This is called a
