EIT image of a solar flare
Active region 10486 on the Sun, which was already under close scrutiny by several instruments on board SOHO and other satellites, as well as numerous ground observatories, started up a spectacular two-part show in the morning on Tuesday 28 October 2003.
An X 17.2 flare, the second largest flare observed by SOHO, set off a strong high energy proton event and a fast-moving Coronal Mass Ejection (CME), hitting the Earth early on Wednesday 29 October. The encore came on Wednesday afternoon, when an X 10.0 flare from the same active region set off another round of particles and another fast-moving CME.
This image from the Extreme ultraviolet Imaging Telescope (EIT) on board SOHO shows the first of the two flares. It was taken on 28 October 2003, at 11:12 UT, through a filter centred at 195 Ångström.
See the related images for another EIT image taken several hours later, when the instrument was showered in the ensuing storm of energetic particles from the Sun.