Earth, Wind & Fire

Geomagnetic storms have had severe impacts on Earth. A 1989 storm caused by a CME resulted in the collapse of the Hydro-Quebec’s electricity transmission system, causing six million Canadians to lose power. In 1859 a solar storm called the Carrington Event produced auroras from the North Pole to Central America and disrupted telegraph communications, even sparking fires at telegraph offices that caused several deaths.

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A team led by the University of Colorado Boulder has found the mechanism behind the sudden onset of a “natural thermostat” in Earth’s upper atmosphere that dramatically cools the air after it has been heated by violent solar activity.

Scientists have known that solar flares and coronal mass ejections (CMEs) — which release electrically charged plasma from the sun — can damage satellites, cause power outages on Earth and disrupt GPS service. CMEs are powerful enough to send billions of tons of solar particles screaming toward Earth at more than 1 million miles per hour, said CU Boulder Professor Delores Knipp of the Department of Aerospace Engineering Sciences.

Now, Knipp and her team have determined that when such powerful CMEs come off the sun and speed toward Earth, they create shock waves much like supersonic aircraft create sonic booms. While the shock waves from CMEs pour energy into Earth’s upper atmosphere, puffing it up and heating it, they also cause the formation of the trace chemical nitric oxide, which then rapidly cools and shrinks it, she said.

“What’s new is that we have determined the circumstances under which the upper atmosphere goes into this almost overcooling mode following significant heating,” said Knipp, also a member of CU Boulder’s Colorado Center for Astrodynamics Research. “It’s a bit like having a stuck thermostat — it’s really a case of nature reining itself in.”

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