Thanks to some state-of-the-art instruments, NASA scientists caught a surprisingly wicked glimpse of Earth’s radiation belts, providing a better understanding of how they coexist with one-another in (relative) harmony. The key is all in being able to tell protons from electrons — pluses from minuses.
The Van Allen Probes are two NASA spacecraft launched into Earth’s radiation belts, beyond the lower orbit — exposing them to harsh cosmic rays and solar storms. For this reason, the probes are designed to go into a safe mode to avoid damage to the crafts. The probes glide through the belts constantly collecting data for NASA’s Living With A Star Program, which aims to understand the particle make-up of the belts so scientists can plan missions accordingly.
“The spacecraft plunge through the radiation belts five to six times a day on a highly elliptical orbit, in order to understand the physical processes that add and remove electrons from the region,” NASA said.
In June 2015, a geomagnetic storm was so strong, it caused relativistic electrons from the outer belt to sink deep into the inner belt. This significant event was recorded by the probes using their magnetic electron and ion spectrometers. This tool works by creating its own magnetic field that allows it to siphon in particles from the belts and divvy them up.
The relativistic electrons were so powerful that they were easily distinguished by the probes. Typically, the protons are much more powerful than any low-energy electrons usually floating around the inner belt, so they contaminate the results. But, when this storm hit, they understood that the inner belt has much lower radiation than previously thought, and it is really only heightened during very intense, and very rare, storms. You can see this reaction to storms in the video.
In the grand scheme of space exploration, this means scientists can design lighter, cheaper crafts to orbit in this region without fear of them being destroyed by radiation.
This new understanding also makes it easier for human space travel, namely because NASA is hesitant to send astronauts outside of Earth’s lower orbit for fear of radiation exposure. It’s one of the more pressing reasons we haven’t yet sent a human to Mars. This new data is an important step in helping to assess and solve that problem.