The curious case of colourful Northern Lights

Scientists have, for the first time, directly observed the shower of electrons bouncing across Earth’s magnetic field, which causes the spectacular, colourful phenomenon commonly known as the Northern Lights.

While the cause of these colourful auroras has long been hypothesised, researchers had never directly observed the underlying mechanism until now. The spectacle of these subatomic showers is legendary. Green, red, and purple waltz across the night sky, blending into one another for a fantastic show widely considered one of the great wonders of the world.

Among a variety of auroras, pulsating auroral patches appearing at dawn are common but the physical mechanisms driving this auroral pulsation had so far not been verified through observation.

With the advent of a new satellite with advanced measuring tools, researchers have now identified that this wonder is caused by the hard-to-detect interaction between electrons and plasma waves.

This interaction takes place in the Earth’s magnetosphere, the region surrounding the Earth in which the behaviours of the electric particles is usually governed by the planet’s magnetic field.

The global reconfiguration often drives a specific type of plasma waves called chorus waves, to rain electrons into the upper atmosphere. This stabilises the system, and gives off a colourful light as the electrons fall. However, scientists have questioned if the chorus waves were powerful enough to excite electrons to the extent of creating auroras.