The Sun radiates more than just life-sustaining light into the solar system. At irregular intervals, it also produces bursts of high-energy particles. These solar particles have energies that range from 30,000 electron volts to 30 billion electron volts per nucleon and consist primarily of protons (96% of the total number of nuclei) and helium nuclei (3%). The remaining particles are ions of elements that are common in the solar atmosphere, such as carbon, nitrogen, oxygen, neon, magnesium, silicon, and iron, as well as small numbers of even heavier elements. The processes that produce high-energy protons and ions also accelerate electrons to at least 20 million electron volts. Collisions between energetic particles and the solar atmosphere also produce neutrons and gamma rays. All these particles flow outward from the Sun into the heliosphere, where they can affect space systems and are a major concern for astronaut safety.

The Origins of Solar Particles