chapter  7
Natural Radiation
Pages 16

The atmosphere is continuously exposed to particles from outer space. A stream of particles consisting of protons (about 85% ), α-particles (about 13%), and a small fraction of larger particles hit the outer atmosphere. Some of the particles have very large energies when hitting the atmosphere (up to 1014 MeV). When the particles interact with the atoms in the atmosphere their energy gradually decreases and a number of new high energy particles are formed.