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Right before auroras dance in the sky, there’s often an appearance of a mysterious shape.

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It drapes across the sky like a glowing pearl necklace.

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Scientists call them auroral beads.

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Structures like these can reveal how Earth’s magnetic field

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interacts with solar material gushing through space.

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Understanding these interactions better could help scientists protect

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low-Earth orbiting satellites from extreme solar events.

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But, until now, how the beads form has been a mystery.

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With the help of NASA satellites and computer models,

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scientists have the first evidence of how auroral beads form.

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All auroras are created when charged particles from the Sun

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 are first trapped in Earth’s magnetic environment

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and are then funneled into the atmosphere.

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But scientists are now realizing that small changes in the magnetic environment

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can cause big differences in how the aurora can look.  

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To analyze the auroral beads in more detail,

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scientists took observations from NASA’s THEMIS mission.

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Three of the THEMIS spacecraft study near-Earth phenomena that triggers auroras.

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Scientists then combined THEMIS observations with ground measurements

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and powerful computer models.

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This is the result.

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It’s a simulation of the near-Earth environment

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that scientists can  analyze on scales from tens of miles to 1.2 million miles.

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They found that when particularly large streaming clouds of plasma from the Sun

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reached Earth’s magnetic field,

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they created buoyant bubbles of plasma behind the planet.

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Just like a lava lamp, the buoyancy between the bubbles

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and heavier plasma creates fingers of plasma about 2,500 miles wide

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that stretch down towards Earth

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creating the distinct pearl necklace structure in auroral beads.

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From the ground the beads average about 30 miles wide.

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Scientists hope these models will also be able to explain

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other small-scale structures seen in the auroras.

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The new results show us that even small, short-lived events within auroras

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can be linked to big, global phenomena in our near-Earth environment.

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