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Keywords:

  • global simulations;
  • soft electron precipitation;
  • thermospheric mass density enhancement

From 2000 to 2010, a German satellite carrying the Challenging Minisatellite Payload (CHAMP) orbited the Earth, tracking the properties of the thermosphere—the atmospheric layer that starts roughly 90 kilometers above the surface and coincides with the lower layers of the ionosphere. In analyzing CHAMP's observations, researchers came across an anomaly: 400 kilometers above the Earth in two different regions in the thermosphere, the density was persistently higher than scientists expected given model calculations. The density enhancements were found in two places: at the dayside cusp—the polar region where terrestrial magnetic field lines create a funnel for the solar wind—and in the auroral region on the planet's nightside. Though researchers had identified these anomalous regions, they have so far been unable to identify a mechanism to explain them.