Modulation of Galactic Cosmic Rays

Abstract

As already noted in §10, the energy distribution of fast particles in interplanetary space is continuous. The lowest energy corresponds to the energy of solar wind plasma particles. The energy of the most energetic particles detected in extensive atmospheric showers exceeds 10²⁰ eV. In this enormous energy range it is impossible to determine the exact critical energy which separates solar and galactic cosmic rays. However, since particles with T > T₀ = 10 GeV per nucleon are very seldom detected in solar events, one may conventionally assume that all particles with T > T₀ are of galactic origin. The nature of particles with lower energy is not entirely clear. According to estimates by Hayakawa (1969), particles of solar origin produce 10% of the total cosmic ray intensity in the solar system. The fraction of solar particles is likely to increase with decreasing energy.