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Earth\u2019s 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.<\/p>\n
This captive swarm of charged particles plays an important role in how Earth reacts to changing conditions in space, called\u00a0space 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.<\/p>\n
NASA is preparing to launch a mission designed to provide a unique, inside-out view of the ring\u00a0current. Called\u00a0STORIE (Storm Time O+ Ring current Imaging Evolution), it is scheduled to launch in May aboard\u00a0the 34th SpaceX commercial resupply services mission to the International Space Station for NASA. The mission is flying as part of the Space Test Program \u2013 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\u00a0and what kind of particles it\u2019s made of.<\/p>\n
\u201cThese particles\u00a0have important space weather impacts,\u201d said Alex Glocer, STORIE\u2019s principal investigator at NASA\u2019s Goddard Space Flight Center in Greenbelt, Maryland, where the instrument was designed and constructed. \u201cWe want to understand how that trapped population is built up, and where it comes from.\u201d<\/p>\n
These details are especially important during solar storms, when outbursts from the Sun can lead to magnetic disturbances at Earth.\u00a0Similar to Earth\u2019s\u00a0Van Allen radiation belts\u00a0but 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.<\/p>\n
However, it\u2019s difficult to study the ring current directly because the particles within it are invisible. \u201cYou can\u2019t just image them with a camera,\u201d Glocer explained.<\/p>\n
Instead, STORIE will scan for the glow of energetic neutral atoms, or ENAs, that are formed when charged particles trapped in the ring current manage to escape. The particles\u00a0earn\u00a0their freedom by stealing an electron from Earth\u2019s outer atmosphere, known as the exosphere, and become neutral.\u00a0<\/p>\n
\u201cOnce those charged particles become neutral, they no longer feel the effects of Earth\u2019s magnetic field, and they are no longer trapped,\u201d Glocer said. \u201cThey can just fly off in any direction.\u201d<\/p>\n
By measuring the speed and direction of the ENAs, STORIE could help answer longstanding questions about the\u00a0origins\u00a0of particles in the ring current \u2014 whether they are supplied by a stream of particles flowing out from the Sun, known as the solar wind, or from Earth.<\/p>\n
The STORIE team designed the instrument to pay special attention to positively charged oxygen atoms (O+) because, according to Glocer, \u201cWhen you see oxygen, that comes from the atmosphere. You get very little of that from the solar wind.\u201d If STORIE finds a lot of oxygen atoms, scientists will know the ring current is largely supplied by Earth\u2019s atmosphere, rather than the solar wind.<\/p>\n
Glocer and other scientists also want to find out whether the ring current\u2019s population of charged particles build up in quick bursts or slowly and gradually. \u201cIs it like filling a lake with the steady flow of a waterfall or a bunch of raindrops?\u201d\u00a0Glocer said.<\/p>\n \n