A Discussion on solar studies with special reference to space observations - Solar particle events

In the last few years, the very sensitive detectors on board satellites and space probes have revealed that the emission of particles from the Sun is a much more frequent phenomenon than had been supposed before, and that the recorded particle events greatly differ as to their character. The following scheme tries to demonstrate the variety of phenomena we meet with when speaking about particle emission from the Sun: Permanent emission of protons with energy close to and below 1 MeV is associated with some specific active regions. Spacecraft detect it on about the second day after the appearance of the region on the eastern solar limb and particles are then recorded permanently until the region moves to about 40° behind the western limb (Fan et al. 1968). It is not yet clear whether this flux manifests a permanent acceleration of particles in the active region or a storage of lowenergy particles in space remaining there as remnants of individual discrete particle events. In any case, however, these active regions are the seats of discrete particle events, and thus they represent regions where favourable conditions for acceleration processes have been formed (Svestka 1970 a).