COSMIC RAYS AND SOLAR PROTONS IN THE NEAR-EARTH ENVIRONMENT AND THEIR ENTRY INTO THE MAGNETOSPHERE

Energetic solar particle events (SPE) and galactic cosmic rays (GCR) can have a significant effect on the design and operations of interplanetary and earth-orbiting spacecraft. They produce high energy protons and heavier ions, which can cause radiation degradation of electronic parts, sensor interference and single event effects. Although both environments are modulated by solar activity effects, GCR fluxes are always present while SPEs occur sporadically throughout the solar cycle. A description of the particle fluxes is presented in terms of their source, acceleration mechanisms, energy spectra and composition, directionality, transport through interplanetary space to the boundary of the earth’s magnetosphere and finally through the magnetosphere to lower altitudes. The relevance of both sets of particle fluxes is discussed in the context of Space Weather. Emphasis is given to the underlying physical processes involved but current engineering models and their inadequacies are also discussed. The prospects for prediction are addressed in terms of our present state of knowledge, including the issues involved in separating causes from associations. 1