Researchers Reveal the Source of the Electron Rain Phenomenon

Scientists from the University of California, Los Angeles (UCLA) discovered the source of the super-fast, energetic electron rain, as stated in a press release. The phenomenon that contributes to the amazing aurora borealis can also be hazardous to astronauts and space instruments.

The electron rain was observed from low-Earth orbit by the Electron Losses and Fields Investigation (ELFIN) mission, a pair of tiny satellites intended to explore space weather. The UCLA scientists used ELFIN data, as well as information from past NASA observations, to discover that the rainfall was caused by whistler waves, a type of electromagnetic wave that flows across space plasma.

They point out in their findings published in Nature Communications that whistle waves cause more electron showers than existing theories and space weather models have predicted.

Xiaojia Zhang, the paper’s lead author, said, “ELFIN is the first satellite to measure these super-fast electrons.” She added that the mission was yielding new insights due to its unique vantage point in the chain of events that produced them.

The process of electron rain

Electron rain happens in the space environment close to Earth, which is densely packed with highly charged particles orbiting the planet. These areas are known as the Van Allen radiation belts.

The study looks at how whistler waves, under specific conditions and produced within radiation belts, energize and accelerate electrons. It induces electron paths to enlarge, forcing them to burst out of the belts and precipitate, resulting in the electron shower.

Credits: Zhang, et al., Nature Communications, 2022

The UCLA professor of space physics, Vassilis Angelopolous, describes the Van Allen belts as huge containers loaded with water. When strong waves strike the water in the containers, it will spill swiftly in large volumes from the containers’ edge. Since ELFIN is both downstream and upstream of the electron flow, the satellites can accurately measure the flow.

“Data from the ELFIN satellites are at the cutting edge of space weather studies and will be heavily used by researchers around the world over the next decade,” said Ethan Tsai, the co-author and project manager at UCLA. “So we’ve worked very hard to make our data open and easily accessible to the entire space science community.”

This research is considered important and adds up to a significant contribution because the leading theories do not predict phenomena like whistler waves in electron flows. Not to mention that the electron downpour can affect the chemical composition of the Earth’s atmosphere and endanger the space equipment up there.