Cosmic rays

Cosmic rays are energetic charged particles (protons). The Solar System (including Earth) is exposed to a steady ionizing radiation flux that is very nearly uniform in all directions. [Cosmic rays should not be confused with the solar wind that originates in the Sun]. The most energetic cosmic rays come from beyond our galaxy.

An individual high energy proton interacts with an atom in the high atmosphere, leading to one, and then many, cascades of nuclear fragments that eventually reach ground level. The most energetic nuclear interactions ever encountered have been occasional very energetic cosmic ray collisions, detected indirectly at ground level, as a derived shower over a wide area.

Secondary cosmic rays (mostly gamma rays) are part of the background ionizing radiation at ground level. They make a small Geiger Counter tick intermittently. People living at altitude have an increased lifetime radiation dose from this source, and pilots probably get more than is good for them.

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