Chapter 13 - Near-Earth Radiation Environment for Extreme Solar and Geomagnetic Conditions

Abstract

The near-Earth environment can be considered a unique place where different space radiation fields exist and can play a significant role in the estimation of radiation risks both for robotic and manned space missions. One cannot exclude the cumulative effect for particular spacecraft orbits the result of simultaneous impact of the different radiation fields. Among the types of space radiation, we consider: trapped radiation at low Earth orbits (LEO): solar energetic particles (SEP) penetration in the magnetosphere, including ground level enhancement events (GLE); and variations of galactic cosmic rays (GCR) during the different extreme levels of geomagnetic and solar activity. Results of empirical modeling of these different radiation fields and some results of measurements of their physical parameters (energy spectra, space and time variations) for different solar (extreme solar maxima and solar minima) and geomagnetic (the major magnetic storms) conditions are analyzed. The models are based on quantitative relationships between the particle fluxes, taking into account the solar activity (sunspot numbers). Examples of using these models to estimate changes of radiation hazards in interplanetary space for the possible case of solar activity reduction during the nearest solar cycles 25 and 26 are analyzed.