A special type of aurora, draped east-west across the night sky like a glowing pearl necklace, is helping scientists better understand the science of auroras and their powerful drivers out in space. Known as auroral beads, these lights often show up just before large auroral displays, which are caused by electrical storms in space called substorms. Previously, scientists weren’t sure if auroral beads are somehow connected to other auroral displays as a phenomenon in space that precedes substorms, or if they are caused by disturbances closer to Earth’s atmosphere.
But powerful new computer models combined with observations from NASA’s Time History of Events and Macroscale Interactions during Substorms—THEMIS—mission have provided the first strong evidence of the events in space that lead to the appearance of these beads, and demonstrated the important role they play in our near space environment.
“Now we know for certain that the formation of these beads is part of a process that precedes the triggering of a substorm in space,” said Vassilis Angelopoulos, principal investigator of THEMIS at the University of California, Los Angeles. “This is an important new piece of the puzzle.”
By providing a broader picture than can be seen with the three THEMIS spacecraft or ground observations alone, the new models have shown that auroral beads are caused by turbulence in the plasma—a fourth state of matter, made up of gaseous and highly conductive charged particles—surrounding Earth. The results, recently published in the journals Geophysical Research Letters and Journal of Geophysical Research: Space Physics, will ultimately help scientists better understand the full range of swirling structures seen in the auroras.
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Courtesy of Mara Johnson-Groh, NASA’s Goddard Space Flight Center
