Video: Magnetic eruption

A solar flare plus a giant magnetic filament may spell trouble for satellites (Image: NASA)

An unusually complex magnetic eruption on the sun has flung a large cloud of electrically charged particles towards Earth. When the cloud hits, which could be anytime now, it could spark aurorae in the skies around the poles and pose a threat to satellites – though probably not a particularly severe one.

On 1 August, a small solar flare erupted above sunspot 1092. It would not have raised many eyebrows, except that a large filament of cool gas stretching across the sun’s northern hemisphere also chose that moment to explode into space.

Despite being separated by hundreds of thousands of kilometres, the two events may be linked. Images from NASA’s Solar Dynamics Observatory hint at a shock wave travelling from the flare into the filament. “These are two distinct phenomena but they are obviously related,” says Len Culhane, a solar physicist at the Mullard Space Science Laboratory, University College London.


Satellite threat

Filaments are gigantic tubes of magnetism that fill up with solar gas and hang in the atmosphere of the sun. This particular one spanned 50 times the diameter of our planet before it burst. It then spilled its contents into space, producing a cloud of electrically charged particles known as a coronal mass ejection.

When the cloud hits our planet, as will happen any day now, satellites could be affected. A gust of solar particles in April may have been responsible for putting Intelsat’s Galaxy 15 permanently out of action.

In the grand scheme of solar things, this is not a big eruption. The sun is currently rousing from an unusually extended period of quiet. “If the solar activity continues to rise, then in three to four years this will be seen as a comparatively normal event,” says Culhane.