The Earth's upper atmosphere has had a record breaking collapse, one that has scientists both puzzled and worried, NASA announced Thursday. The collapse occurred during a period of low solar activity known as a "solar minimum." During a solar minimum, sunspots and solar flare activity heavily diminish. Since the date range of a solar minimum expands over a 12-month period, it can take up to 6 months to identify one.
This collapse occurred during the 2008-2009 solar minimum. While these minimums are known to cool and contract the thermosphere, this collapse was 3-times greater than low solar activity could explain.
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