Sympathetic flare event, October 2002

These Hydrogen-alpha images show a pair of solar flares that erupted within seconds of each other on opposite sides of the Sun on 31 October 2002. The images were taken by the prototype unit of the Improved Solar Observing Optical Network (ISOON) at Sacramento Peak. Known as a sympathetic flare event, such a confluence can occur when two active regions on the sun are energized and were on the verge of erupting anyway, according to Dr. Donald Neidig, ISOON project manager. If they are connected by magnetic flux tubes, the eruption of one can trigger the other within seconds, or a third, less powerful, event, can trigger two more powerful active regions to go off at the same time. This particular one is unique in that the two flares are on almost opposite sides of the solar disk, about 2.2 million kilometers apart. Since the two appeared at almost the same instant, this suggests that something triggered them. This discussion is from the December 2002 NSO Newsletter (currently only available in PDF format): for further information, see http://www.nso.edu/press/flare/.