Cosmic Rays as Electrical Particles

Abstract

Positive evidence that the primary cosmic rays consist of electrical particles is drawn from three types of experiments:1. Latitude and directional asymmetry effects. Clay finds 83 percent as intense ionization at the equatorial minimum as in high latitudes. Of the remainder, Rossi's directional experiments show that about 12 percent at least is due to positively charged particles. Corresponding to the 73 percent "nonfield sensitive" remainder at sea level, at high altitudes the remainder must be less than 20 percent, perhaps no more than 2 percent, of that observable in polar regions. An energy distribution analysis, following the method of Zanstra, but using new latitude effect data collected on the Pacific Ocean in collaboration with R. N. Turner, shows a continuous energy distribution of the primary cosmic-ray particles between 0.9 and 1.9\ifmmode\times\else\texttimes\fi{}${10}^{10}$ ev, and indicates the electrical particle origin of a large part, very possibly the whole of the ionization.2. Coincidence experiments. Auger, Street and their collaborators have proved that most of the multiple coincidences observed with counter tubes are caused by single high energy ionizing (hence electrical) particles. Experiments by Rossi and Hsiung show that these coincidence producing particles are not secondaries, but originate beyond the atmosphere. Likewise latitude effect experiments by Johnson and absorption experiments by Rossi indicate that the shower producing radiation is produced by electrical primaries. Cloud chamber studies show that almost all of the observed cosmic-ray ionization is due either to particles of the coincidence type or to showers, and is hence ascribable to electrical primaries.3. Galactic rotation effect. A directional asymmetry of cosmic rays ascribable to the motion of the earth with the rotation of the galaxy, seems to be established by sidereal time variations very recently reported for the northern hemisphere by Illing and for the southern hemisphere by Schonland, Delatizky and Gaskell, and by a new provisional observation by Compton and Turner of a difference of 0.6 percent between the northern and southern hemispheres. These results are in quantitative agreement with the approximate predictions of Compton and Getting based upon electrically charged primaries; but the observed diurnal effect is only about $\frac{1}{7}\mathrm{th}$ as great as is to be expected if the primary cosmic rays are photons. The data are thus difficult to reconcile with more than a few percent of primary photons.Two lines of positive evidence for photon primaries have been put forward. 1. The flattening of the altitude vs. ionization curves at very high altitudes, once interpreted as indicating the gradual growth of secondary ionization as primary photons enter the atmosphere, has been shown by later balloon flights at different latitudes to be a geomagnetic phenomenon, indicating that the corresponding portion of the radiation is electrical in character. 2. Certain high energy nonionizing shower producing rays shown in cloud photographs by Anderson and his collaborators have been ascribed to primary photons. A more detailed examination of the photographs in question, however, seems to show that these shower producing rays are definitely of local and hence secondary origin. The arguments that have been raised by Bowen, Millikan and Neher against the explanation of cosmicray ionization as due to electrically charged primaries are all found to have a straightforward answer if we assume the correctness of current theories which make photon production the chief mechanism whereby a cosmic-ray electron loses its energy. The conclusion is drawn that primary photons are not responsible for any of the major features of the cosmic rays as we now know them. It seems necessary to assume the presence of both positive and negative electrons among the primaries. There is also some suggestion of the existence of protons.