When high-energy particles flying in outer space (cosmic rays) impact the Earth's atmosphere, they cause nuclear reactions to produce neutrons—called cosmic ray-induced neutrons.
The Earth is unceasingly bombarded by a variety of particles from outer space. These particles, when causing nuclear reactions with the atomic nuclei of oxygen and nitrogen, etc. in the Earth's atmosphere, generate many particles including protons and neutrons. The neutrons generated in this way are called cosmic ray-induced neutrons. When these particles reach the surface of the earth, the cosmic ray-induced neutrons pass through human bodies and buildings, etc. to plunge into the ground.
It is known that cosmic ray-induced neutrons cause soft errors by clashing with semiconductors and memory chips installed inside electronic equipment.