Earth witnesses 'polar rain' aurora for the first time
In a first, Earth experienced a unique aurora due to a significant decrease in solar wind gusts. This rare spectacle, termed as 'polar rain,' was caused by an electron 'rainstorm' from the Sun. The phenomenon was discovered by researchers based in Japan and the United States, after two years of study focusing on mysterious green auroras, that appeared in the Arctic on December 25, 2022.
How are auroras formed?
Typically, auroras are powered by electrons from solar wind and exhibit discernible shapes that pulsate across the sky. These electrons get trapped in Earth's magnetotail, an extension of our planet's magnetic field. During extreme space weather conditions such as a coronal mass ejection (CME), these trapped electrons flow down to Earth's poles and collide with atmospheric molecules, causing them to glow in various colors.
The Christmas aurora: A unique spectacle
The Christmas aurora of 2022, however, was notably different from typical auroras. Captured by an All-Sky Electron Multiplying Charge-Coupled Device (EMCCD) camera in Longyearbyen, Norway, this aurora appeared as a faint and featureless glow spanning 3,999km. Unlike its counterparts, it lacked structure and did not pulsate or vary in brightness. This type of aurora had never been observed from Earth before.
Solving the mystery of the unusual aurora
The enigma of this unusual aurora was unraveled by a team headed by Keisuke Hosokawa from the Center for Space Science and Radio Engineering, at the University of Electro-Communications in Tokyo. The team compared data from the Special Sensor Ultraviolet Scanning Imager (SSUSI) on polar-orbiting satellites of the Defence Meteorological Satellite Program (DMSP) with observations of the unique aurora. This comparison helped them understand this unprecedented 'polar rain' phenomenon.
