Even the most powerful flares are barely detectable in the total solar irradiance (the 'solar constant'). Powerful flares are often, but not always, accompanied by a coronal mass ejection. Seen here from the Solar Dynamics Observatory, the flare caused auroras to be seen on Earth on September 3.Ī solar flare is a sudden flash of increased brightness on the Sun, usually observed near its surfaceĪnd in close proximity to a sunspot group. On August 31, 2012, a long prominence/filament of solar material that had been hovering in the Sun's atmosphere, the corona, erupted out into space at 4:36 p.m.