Stormy Sun

A coronal mass ejection

A huge explosion from the surface of the Sun, known as a coronal mass ejection. (The direct light from the Sun has been blocked out by the black disc; the white circle shows the size of the Sun.)

  • Coronal mass ejection, a huge solar explosion
  • Can expel a billion tonnes of matter
  • Moves at 1.5 million kilometres per hour

Solar storms bombard Earth with a stream of electrons and other charged particles that interact with gases in our atmosphere to generate colourful aurora.

A coronal mass ejection, a large solar storm, can expel a billion tonnes of matter at a 1.5 million kilometres per hour or more.

The strongest solar storms have the potential to interfere with communications, power grids, and satellites. Solar storms happen most frequently when the Sun is in the active phase of its 11-year cycle, called solar maximum.

Though the Sun was expected to be entering solar maximum in 2010, it had been unusually quiet for at least two years. Despite its relative lack of activity, the Sun released a series of four coronal mass ejections between May 22 and May 24, 2010.

The images above and below show one coronal mass ejection on May 23.

Both images were taken by the Solar Terrestrial Relations Observations (STEREO) Ahead spacecraft. The top image is from 20:09:15 Universal Time (UT). STEREO Ahead acquired the other image just over two hours later at 22:24:00 UT.

A coronal mass ejection

In this image taken two hours after the first one, the coronal mass ejection can be seen streaming away from the Sun.

In the top image, a bright mass of charged particles loops from the Sun’s atmosphere. In the second image, the looped mass had expanded and was moving away from the Sun.

See the full-size images here and here (will open in new windows).

The images show only the Sun’s corona, the outermost layer of the atmosphere. A dark disc covers the rest of the Sun, and a white circle represents the Sun’s surface.

When the charged particles from May’s coronal mass ejections reached Earth, they caused no damage, but they did generate sheets of coloured light dancing across polar skies.

NASA images courtesy the Solar Terrestrial Relations Observatory Team. Text adapted from information issued by Holli Riebeek.

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