Space weather, i.e. the conditions arising from the Sun's varying activity, implies a whole ensemble of generated electromagnetic and particle radiation. Spatial and temporal factors including the solar cycle and changes in the Earth’s magnetic field modulate the intensities of all types of radiation, also the one coming from outside the Solar system. Several physical phenomena can be connected to Space Weather, including geomagnetic storms, ionospheric disturbances, scintillation of satellite-to-ground radio signals and long-range radar signals, aurora and geomagnetic induced currents at Earth's surface influencing power grids, pipelines and drilling operations. In the atmosphere and in deep space, radiation can damage electronics on board spacecraft, solar cells, heat shields, detectors and can threaten the lifes of astronauts. In particular, the danger becomes increasingly more substantial when moving far away from Earth’s protection e.g. a future manned missions to an asteroid, or to Mars or a mission through the harsh radiation environment of Jupiter and its moons. In general, There are three main sources of particle radiation:
Solar particle radiation: it consists of both low energy solar wind particles flowing constantly from the Sun and of Solar Energetic Particles (SEPs), originating from transient Solar Particle Events (SPEs), linked to wide and high-speed Coronal Mass Ejections (CMEs). SEPs come as huge injections and are composed predominantly of protons and electrons. Typical proton energies range from 10 to hundreds of MeV.
Galactic Cosmic Rays (GCRs): they originate from outside the solar system from the explosion of distant supernovae. The GCRs spectrum consists of approximately 87% hydrogen ions (protons) and 12% helium ions (α-particles), with the remaining 1%–2% of particles being HZE nuclei, with energies between several tenths up to 1010 GeV/nucleon. The large ionization power of GCR ions makes them a major health threat to astronauts for missions beyond near-earth environment. The fluence of ionized nuclei that make up GCR is inversely proportional to the solar cycle and decreases by a factor of two during solar maximum.
Trapped radiation: such particles are produced mainly by interaction of GCR and SPE with the Earth’s atmosphere and are trapped by its magnetic field into the Van Allen radiation belts that comprises a stable inner belt of trapped protons and electrons (energies are between keV and 100MeV), and a less stable outer electron belt. The Earth’s trapped radiation belts are time- depending on the conditions in near-Earth interplanetary space.
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