Earth’s magnetic field is like a powerful trap. It lures electrically charged particles in space, near our planet, and snares them in an invisible, doughnut-shaped pen around Earth known as the ring current.
This captive swarm of charged particles plays an important role in how Earth reacts to changing conditions in space, called space weather, which can affect the technology we rely on, such as satellites and power grids. Yet there is still a lot we do not know about the ring current.
NASA is preparing to launch a mission designed to provide a unique, inside-out view of the ring current. Called STORIE (Storm Time O+ Ring current Imaging Evolution), it is scheduled to launch in May aboard the 34th SpaceX commercial resupply services mission to the International Space Station for NASA. The mission is flying as part of the Space Test Program – Houston 11 (STP-H11) payload, a partnership between the U.S. Space Force and NASA. Once it is robotically installed on the exterior of the space station (expected a few days after its arrival), STORIE will look outward at the ring current, helping scientists answer longstanding questions about how it grows and shrinks and what kind of particles it’s made of.
The ring current is an invisible, doughnut-shaped swarm of charged particles around Earth (shown here in blue). It overlaps the outer of two Van Allen radiation belts (which are shown in green), but the ring current contains lower-energy particles than the radiation belts. In the ring current, positively charged particles and negatively charged particles flow in opposite directions, creating electrical currents. Changes in the ring current influence how our planet responds to solar storms and can have impacts on our technology.
NASA/Mary Pat Hrybyk-Keith/Kristen Perrin
“These particles have important space weather impacts,” said Alex Glocer, STORIE’s principal investigator at NASA’s Goddard Space Flight Center in Greenbelt, Maryland, where the instrument was designed and constructed. “We want to understand how that trapped population is built up, and where it comes from.”
These details are especially important during solar storms, when outbursts from the Sun can lead to magnetic disturbances at Earth. Similar to Earth’s Van Allen radiation belts but filled with lower-energy particles, the ring current tends to fluctuate in size, shape, and intensity more dramatically than the radiation belts do during solar storms. Plus, in the ring current, positively charged particles and negatively charged particles flow in opposite directions, creating electrical currents. So, changes there can lead to magnetic fluctuations and induced currents on the ground, potentially affecting pipelines and power lines. The ring current can also contribute to charge buildup on the surface of Earth-orbiting satellites, which can spark spacecraft glitches. Additionally, when energy ramps up in the ring current, some of that energy gets transferred to the upper atmosphere, making it heat up, puff out, and create more drag on satellites, which can cause the spacecraft to deorbit sooner than expected.
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