The origin of ultrafast substorm auroras
This animation depicts the sequence of events that give rise to ultrafast substorm auroras.
A magnetic reconnection event occurs far out in the magnetotail, at a distance of around 125 000 - 200 000 km.
Energy from this event is transported by kinetic Alfvén waves (KAW) - which carry electrons - towards Earth at speeds of several thousand kilometres per second.
These KAW can reach Earth quickly enough, and carry sufficient energy, to produce intense auroras.
In reality, the reconnection process is persistent and less bursty, continuously emitting energy via the KAWs to the aurora.