the sun at the time of these flares. The peak intensity near the earth's orbit may be much higher than that of the galactic cosmic-ray background. There is evidence that the radiations originating in solar flares consist of particles usually having nonrelativistic velocities, but at times with energies extending well up into the relativistic range. GALACTIC COSMIC RAYS The first component, the galactic background, has been studied for many years with high-altitude balloons and rockets at the top of the earth's atmosphere. From these measurements and from consideration of the earth's magnetic field as a momentum selector, the energy spectrum and particle composition of the primary particles were deduced and are now quite well known. These galactic cosmic rays are known to consist of atomic nuclei, the electrons having been stripped away. Table I shows the relative abundance of the various chemical elements in the galactic cosmic rays, and for comparison the universal abundances of elements as measured by astronomical techniques. The numbers listed pertain to all particles received, regardless of energy. The energy spectrum of the galactic protons is well represented 0.3