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What is a coronal mass ejection?

16 May 2018, 10:00 UTC
What is a coronal mass ejection?
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Coronal mass ejection of February 27, 2000. A disk is being used to block out the light of the sun. The white circle indicates the sun’s surface. Image via NASA’s SOlar and Heliospheric Observatory (SOHO).
Every so often, the sun burps, with the power of 20 million nuclear bombs. These hiccups are known as coronal mass ejections or CMEs. They are powerful eruptions near the surface of the sun, driven by kinks in the solar magnetic field. The resulting shocks ripple through the solar system and can interrupt satellites and power grids on Earth.
During a CME, enormous bubbles of superheated gas – called plasma – are ejected from the sun. Over the course of several hours, a billion tons of material are lifted off the sun’s surface and accelerated to speeds of a million miles per hour. This can happen several times a day when the sun is most active. During its quieter periods, CMEs occur only about once every five days.
See the sun now, via NASA’s Solar Dynamics Observatory
The underlying cause of CMEs is not well understood. Astronomers agree, however, that the sun’s magnetic field plays a major role. Because the sun is a fluid, turbulence ...

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