I.3                 Cosmic ray environment and effects models

Cosmic ray environment and effects models were originally created by Adams and co­workers at the U.S. Naval Research Laboratory [RD.77], under the name CREME. They provided a comprehensive set of cosmic ray and flare ion LET and energy spectra, including treatment of geomagnetic shielding and material shielding. CREME has been superseded by CREME96 [RD.78]. The major differences to the environment specification are in the inclusion of a model of the cosmic ray environment and its solar­cycle modulation due to Nymmik et al. [RD.79], improved geomagnetic shielding calculation, and more realistic Solar Energetic Particle event (SEP) ion environments (see clause 9.2.3).

The cosmic ray fluxes are anti­correlated with solar activity so the highest cosmic ray fluxes occur at solar minimum.