Sun sends a cloud our way

Ejected from the Sun and heading our way

By BBC News Online science editor Dr David Whitehouse

The Sun has put up a spectacular display with two powerful, so-called X-class flares, going off in close succession from one active region on its surface.

Astronomers believe that this month marks the peak of solar activity during the star's 11-year cycle of activity.

Active region 9026

The flares come from active region number 9026, a large and complex sunspot group that observations show has a convoluted magnetic field associated with it.

Magnetic energy accumulated in the magnetic field becomes twisted and strained as the Sun's surface moves. Eventually the strain becomes too much and the magnetic field collapses resulting in an explosion.

Vast quantities of gas are then explosively heated and ejected. Some strikes the Sun's surface and some is lost into space.

The latest flare was seen to erupt at 1530 GMT on 6 June. Soon afterwards, the Sun-monitoring Soho satellite detected a gas cloud moving away from the star.

Scientists call this event a "full halo coronal mass ejection", and say that this particular cloud has been ejected in the direction of the Earth, possibly causing aurorae and other geomagnetic disturbances when it reaches us on Thursday or Friday.