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Rotating solar coronal holes and periodic modulation of the upper atmosphere

We report discovery of a solar‐terrestrial connection between rotating solar coronal holes and density variations in Earth's thermosphere. Specifically, during 2005, a 9‐day recurrence of fast streams in the solar wind exists due to solar coronal holes distributed roughly 120 degrees apart in longitude; this periodicity is transmitted to the geospace environment where it modulates geomagnetic activity and thermospheric densities derived from accelerometer measurements on the CHAMP satellite. Our discovery demonstrates a solar‐terrestrial connection that has not been appreciated before, and by its nature is characterized by an element of predictability. Its potential predictability has practical relevance for collision avoidance and other applications affected by density variability in the terrestrial space environment.