An article published in the journal “Geophysical Research Letters” describes a research on the behavior of the ring of particles that surrounds the Earth. Using the measurements taken by the RBSPICE instrument aboard one of NASA’s Van Allen space probes it was possible to establish that high-energy protons in the ring current behave completely different from low-energy protons. It’s a step forward in the understanding of the Earth’s magnetosphere and therefore of the effects it may have on satellites and even the Earth’s surface.
The Van Allen probes were launched in August 2012 with the main purpose of studying the Van Allen belts, two rings – one internal and one external – of electrically charged particles created by the Earth’s magnetic field around the equator. In the outer ring, between about 10,000 and 60,000 kilometers (6,200 to 37,000 miles) above sea level, there’s the ring current, carried by charged ions trapped in this belt.
The RBSPICE (Radiation Belt Storm Probes Ion Composition Experiment) instrument allowed to study the ring current. This phenomenon was hypothesized about a century ago but it was thought to grow and reduce over time. However, the detections carried out allowed to understand that these changes only cover one category of particles.
The ring current is carried by ions, mainly of hydrogen, which means protons. It’s in part composed of high-energy protons and in part of low-energy ones and these two categories of particles showed different behaviors. In particular, the influence of geomagnetic storms, Earth’s magnetosphere disturbances caused by solar activity, turned out to be crucial.
When there’s a geomagnetic storm, low-energy protons enter the area close to the Earth enhancing the ring current. Instead, when there are no storms the ring current is maintained by high-energy protons. In essence, to understand the ring current we need to watch solar activity with its influence on the Earth’s magnetosphere.
This discovery represents a step forward in the understanding of what happens in the van Allen belts. In case of strong geomagnetic storms, satellites are the first to risk being damaged but in extreme cases the effects can reach the surface. Learning more about what’s happening in the magnetosphere can help us to better protect satellites, electrical grids and electronic equipment.
