Galactic Protons Research Articles

Spatial distribution of protons from neutron decay trapped by the geomagnetic field

The neutron sources at the earth due to galactic cosmic rays and solar protons interacting with the terrestrial atmosphere and also due to solar neutrons are examined quantitatively to see if the observed radiation belt protons can be produced by these neutrons. It is shown that solar protons and solar neutrons do not play any important part in producing the trapped protons. It seems that galactic cosmic rays may be able to make the observed high energy inner-belt proton flux near the equator, but it is difficult to see how the fluxes off-equator can be produced without some other mechanism being involved. Also forE ≤ 10 Mev the galactic cosmic-ray source is inadequate to produce the observed fluxes even for the center of the inner belt.

Cosmic Rays in Space

The energetic particle populations observed in the MeV and greater range in interplanetary space are of both galactic and solar origin. The galactic cosmic rays are ever present though strongly modulated by solar activity while the solar cosmic rays are highly variable. Of particular interest in attempting to assess the radiation hazards for long missions is a more detailed knowledge of the charge and energy spectrum of the galactic component. Measurements of hydrogen, helium, and heavy nuclei down to 100 MeV/nuc have been obtained by groups at the University of Minnesota, the University of Chicago, and the Goddard Space Flight Center using balloon borne instrumentations at high altitudes. Results obtained on the IMP-1 satellite have furnished proton and helium data in the region 10 to 100 MeV. These combined data show a differential proton spectrum which has a broad maximum around 400 MeV and is steeply falling towards lower energies. The helium nuclei and protons seem to exhibit the same relative differential rigidity spectrum above 1.5 BeV. Below this rigidity the relative helium spectrum appears to be more rapidly falling than the proton spectrum. The IMP-1 proton results indicate that the galactic proton differential energy spectrum decreases by a factor of 5 going from 70 MeV to 20 MeV. Thus less than 1% of the total galactic cosmic rays appears to be contained in the low energy region below 100 MeV.

Primary Cosmic Rays

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