High‐energy processes, involving a rich variety of accelerated particle phenomena, lie at the core of the solar flare problem. The most direct manifestation these processes are high‐energy radiations, gamma rays, hard X‐rays and neutrons, as well as the accelerated particles themselves, which can be detected in interplanetary space. In the study of astrophysics from the moon, the understanding of these processes should have great importance. The inner solar system environment is strongly influenced by activity on the Sun; the physics of solar flares is of great intrinsic interest; and much high‐energy astrophysics can be learned from investigations of flare physics at high energies.