NASA Van Allen Probe Glimpses How Radiation Belts Become ‘Supercharged’

On March 17, 2015, the Earth was under attack from the Sun.

A great solar flare caused an interplanetary shockwave that rippled through the Earth's magnetic field, creating one of the greatest solar storms in the last decade.

The solar flare, which is called coronal mass ejection of CME, resulted in a geomagnetic storm that shook the Earth's Van Allen radiation belts - the region in the Earth's outer atmosphere held in place by the magnetic field. Fortunately, NASA's Van Allen Probes were there to capture the rare phenomenon on their instruments, which were detailed in a paper published in the Journal of Geophysical Research.

"We study radiation belts because they pose a hazard to spacecraft and astronauts," David Sibeck, the Van Allen Probes mission scientist at NASA's Goddard Space Flight Center in Greenbelt, Maryland, who was not involved in the research, said in a statement.

"If you knew how bad the radiation could get, you would build a better spacecraft to accommodate that."

Because radiation and energy in space could impact Earth's satellites and damage critical technology such as communication instruments, scientists sought to study the complex space environment. NASA launched the twin Van Allen Probes in 2012 to understand the physical processes that create the harsh space environment to enable scientists to develop better models of the radiation belts.

One of the Van Allen Probes happened to be orbiting the belts and caught a glimpse of the event in high resolution. According to the scientists, the spacecraft measured a sudden pulse of electrons energized to extreme speeds - nearly as fast as the speed of light - as the shockwave slammed the radiation belt. Although the shockwave dissipated within minutes, it left behind a "supercharged" or dynamic radiation environment, where the probes detected a big number of higher energy electrons, which lasted for five days.

"The shock injected - meaning it pushed - electrons from outer regions of the magnetosphere deep inside the belt, and in that process, the electrons gained energy," Shri Kanekal, the deputy mission scientist for the Van Allen Probes at Goddard and lead author of the study, said in a statement.

The March 2015 geomagnetic storm was one of the strongest in a decade, but earlier storms were stronger, such as the March 1991 storm, which was so massive it produced long-lived, energized electrons that remained in the radiation belts for many years.