HZE ions

HZE ions are the high-energy nuclei component of galactic cosmic rays (GCRs) which have an electric charge greater than +2. The abbreviation "HZE" comes from high (H) atomic number (Z) and energy (E). HZE ions include the nuclei of all elements heavier than hydrogen (which has a +1 charge) and helium (which has a +2 charge). Each HZE ion consists of a nucleus with no orbiting electrons, meaning that the charge on the ion is the same as the atomic number of the nucleus.

HZE ions are rare compared to protons, for example, composing only 1% of GCRs versus 85% for protons. HZE ions, like other GCRs, travel near the speed of light. Their source is likely to be supernova explosions.

In addition to the HZE ions from cosmic sources, HZE ions are produced by the Sun. During solar flares and other solar storms, HZE ions are sometimes produced in small amounts along with the more typical protons, but their energy level is substantially smaller than HZE ions from cosmic rays.

Space radiation is composed mostly of high-energy protons, helium nuclei, and high-Z high-energy ions (HZE ions). The ionization patterns in molecules, cells, tissues, and the resulting biological insults are distinct from high-energy photon radiation—x-rays and gamma rays, which produce low-linear energy transfer (low-LET) radiation from secondary electrons. While in space, astronauts are exposed to protons, helium nuclei, and HZE ions, as well as secondary radiation from nuclear reactions from spacecraft parts or tissue.

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