Physics of cosmic radiation fields.

This paper glances at the knowledge of composition and energy spectra of galactic cosmic rays and briefly discusses the mechanism of solar modulation and of shielding against these particles by the earth's magnetic field. A short review of the properties of solar particle events is given, in which particles emitted from the sun enter the atmosphere. Particle production in the earth's atmosphere in hadronic and electromagnetic cascades is described and the altitude variations of the different particle components are investigated. Typical energy spectra in the atmosphere are presented for some types of particles.