The Never-Ever-Seen ‘Polar-Rain’ Aurora. How Was the Glow Formed?

Researchers from Japan and the United States have finally determined that the enigmatic green auroras that erupted on Christmas Day in the Arctic in 2022 were caused by a “rainstorm” of electrons that are directed from the Sun. This discovery follows two years of study into the auroras.

Then, the auroras get trapped in an extension of the magnetic field of Earth called the magnetotail.

When there is an extreme condition in the space weather, like when a coronal mass ejection (CME) – which is a large ejection of plasma as well as magnetic field from the Sun – gets released, the magnetotail gets pinched off.

The imprisoned electrons gradually descend to the Earth’s magnetic field line close to the poles.

As it happens, the electrons come into contact with Earth’s atmosphere’s molecules, clash with them, and cause them to shine in various aurora colors.

While doing so, they come into contact with molecules in the Earth’s atmosphere, which collide with them and cause them to glow in aurora-like colors.

What set the Christmas aurora apart from the regular aurora?

When the aurora finally materialized on December 25–26, 2022, it looked quite different.

An All-Sky Electron Multiplying Charge-Coupled Device (EMCCD) camera near Longyearbyen, Norway, captured images of the aurora, which was a faint, featureless glow that stretched 2,485 miles (4,000 kilometers) in length.

The aurora had no structure and did not have any pulsing or varying brightness. Such an aurora was never ever seen before from Earth.

A team led by Keisuke Hosokawa, who is from the Center for Space Science and Radio Engineering at the University of Electro-Communications in Tokyo, solved the mystery behind these aurorae by comparing them with what was seen by the Special Sensor Ultraviolet Scanning Imager (SSUSI) on the polar-orbiting satellites of the Defense Meteorological Satellite Program (DMSP).