In the predawn hours of Aug. 30, 2012, a rocket launched from Florida’s Cape Canaveral Air Force Station. Onboard were two 1,500-pound satellites, the Van Allen Probes. Their mission: to study two concentric, donut-shaped radiation belts that surround Earth.
These belts swell and shrink. According to NASA, the Van Allen Probes travel through the radiation belts at around 2,000 miles per hour. But to understand these belts, scientists are also interested in studying the ring current, an electrical current located approximately 6,200 to 37,000 miles from Earth.
“We study the ring current because, for one thing, it drives a global system of electrical currents both in space and on Earth’s surface, which during intense geomagnetic storms can cause severe damages to our technological systems,” said Matina Gkioulidou, of the Johns Hopkins University Applied Physics Laboratory, in a statement. “It also modifies the magnetic field in near-Earth space, which in turn controls the motion of the radiation belt particles that surround our planet. That means that understanding the dynamics of the ring current really matters in helping us understand how radiation belts evolve as well.”
Now, a paper published in Geophysical Research Letters has compiled data from a continuous year of observations from the ring. And scientists are realizing the rings behave much differently than previously thought.
The data was gathered by the Radiation Belt Storm Probes Ion Composition Experiment.
According to Gkioulidou, changes in the ring current are observable through changes in the Earth’s surface magnetic field. But previous methods only represented the dynamics of low-energy protons.
“Previously, the state of the ring current has been inferred from variations of the Sym-H index,” said Gkioulidou.
Armed with the one-year data, the researchers found presence of a persistent ring current, comprised of high-energy protons. The current was present even when there was a lack of geomagnetic storms. During geomagnetic storms, the current is bolstered by low-energy protons entering the near-Earth region.
Previously, scientists thought the ring current wax and waned, but didn’t establish any delineation between low-energy and high-energy protons, according to NASA.