This is a long-standing problem and nobody has a good solution for it. They are too small to understand with current telescopes, but will be within Solar-B's grasp. Virtually all of the dynamic phenomena we observe on the Sun can be traced back to magnetic fields which form deep in the Sun's interior. These fields can emerge in large active regions that would swallow the entire Earth many times over, or on scales smaller than we can currently see - about 100 km across. As these fields rise, they are twisted and stretched, and store energy much like a rubber band stores energy when it is twisted or stretched.
Most scientists think that the field reconnects.
When a twisted rubber band is cut, the band untwists, leaving two open ends. The magnetic field behaves the same way, but with one important difference. Magnetic field lines can't have open ends, and so if a field line is cut, it has to rapidly reconnect either to itself or to another field line that has undergone a similar process. Links to larger image . The Japanese Solar-B mission will provide the first real opportunity to study this 'reconnection' process, which scientists think releases the tremendous amounts of energy that fuels solar flares.