Identification of a Highly Variable Component in Low-Energy Cosmic Rays at 1 A.U.

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Abstract
Evidence is given for the existence of two distinct populations of cosmic-ray protons and alpha particles in the energy range of 4 to 80 MeV/nucleon: (1) a highly variable component with an inverse energy dependence and (2) a quasisteady "residual" component which shows a positive dependency on energy. The analysis is based on a series of four-day energy spectra obtained from the cosmic-ray experiments aboard IMP-IV during the time interval from 24 May 1967 to 20 August 1968. It is suggested that the highly variable component is probably entirely of solar origin. The "residual" component is most likely of galactic origin although below 10 MeV it may also contain some solar particles.