Search for low-energy interplanetary positrons

Abstract

Preliminary results of an experiment designed to detect and measure the intensity of interplanetary positrons of energy 0–3 MeV with the satellites OGO-I and OGO-III are outlined. Evidence for a statistically significant counting rate of detected positrons is presented, and the possibility that these particles represent a true primary component rather than a background effect, such as cosmic-ray induced secondaries in the detector, is considered. It is shown that the apparent intensity of low-energy positrons, assuming that value derived from their counting rate, would be consistent with an equilibrium charge ratio. This result would not be predicted with mechanisms involving the ionization of matter or the acceleration of electrons, but would be consistent with a strongly energy-dependent galactic trapping parameter allowing meson-decay electrons to slow down in great abundance, or with the existence of an independent source.