Superfast electron rains detected pouring down onto Earth

Researchers at UCLA have discovered a new form of space weather, superfast electron rains that precipitate into the atmosphere from the radiation belts.

The team says the events could affect satellites, spacecraft and astronauts, but aren’t accounted for in current models of space weather.

Electron rains aren’t a new thing, nor are they particularly problematic most of the time. Electrons and other charged particles collect in the Earth’s magnetosphere, bouncing back and forth between the north and south poles. Solar wind and storms can knock some of them loose, sending them raining down into Earth’s atmosphere where they can contribute to aurora.

But in the new study, the UCLA researchers discovered a new mechanism that creates larger downpours of electrons than previously known.

The culprit is what’s known as “whistler waves,” a kind of electromagnetic wave that washes through the plasma in the magnetosphere. These waves can energize the electrons in that plasma, causing them to speed up and fall out of the radiation belts. The resulting rains move much faster and in greater volumes than the usual electron rains.

The team made the observations using ELFIN, a pair of microsatellites each about the size of a loaf of bread. From their position in low-Earth orbit, the ELFIN satellites can detect and measure electron rains, while the team measured whistler waves using data from NASA’s THEMIS satellites. Combining the two datasets indicated a clear link between whistler waves and superfast electron rains. Perhaps unsurprisingly, these downpours occurred more often during solar storms.

So far, these superfast electron rains aren’t accounted for in existing models and predictions for space weather. But factoring them in is important, the team says, because these events can disrupt satellites in low orbit, damage spacecraft passing through, or affect the health of astronauts.