Nuclear Fusion Process in ³He-Rich Flares

Abstract

Hard X-rays associated with solar flares are recently reinterpreted as a thermal emmision from very hot plasma with temperatures more than 10⁸ K. Among ³He-rich flares, May 28, 1969 event has a very clear thermal spectrum of hard X-rays detected by the 0S0-5 satellite. The temperature of the hard X-ray emitting plasma was about 7 × 10⁸ K, much higher temperature as compared with other ordinary flares. Therefore we propose here that a nuclear fusion process takes place within the X-ray emitting plasma itself.

Another author has proposed a nuclear hypothesis (Colgate et al.,1977), which is, however, criticized by some authors because of the unrealistic model of nuclear interaction region in the solar atmosphere. They assumed T = 2 × 10⁹ K and n_e = 3 × 10¹⁵ cm^-3 within a very thin magnetic tube with a radius 70 cm and a length 2×10⁹ cm. Radio emission calcurated by using thier parameters gives an extremely small flux as compared with actually observed radio flux. Our model, on the other hand, requires only a moderate temperature and density observed actually by hard X-rays, giving a reasonable radio flux. Such region can exist stable for several minutes during a flare. An extremely high temperature and density are not needed in our model.