MDI image of active region 10486
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 Michelson Doppler Imager (MDI) on board SOHO shows the Sun's disk on 28 October 2003, at 06:24 UT, a few hours before the first of the two flares. The large group of sunspots of active region 10486, from which the flares later originated, is in the lower left quadrant of the Sun's disk.
A movie showing the evolution of the sunspots on the Sun's disk between 20 and 31 October is available from the right-hand menu under "related videos".