-6- - Cosmic Radiation

Abstract

This chapter analyzes various aspects of cosmic radiation. Cosmic radiation is constituted of stable charged particles and nuclei with lifetimes of 106 years or longer originating from space that strike the top of the atmosphere (TOA) from all directions. Air showers of the cosmic radiation consist of cascades of subatomic particles and electromagnetic radiation resulting from nucleon–nucleon collisions of high-energy cosmic-ray particles from space with atomic nuclei of the earth's atmosphere. Cosmic rays can originate from (1) energetic particles associated with mass ejections from solar flares and similar energetic solar events, (2) anomalous cosmic rays, which are particles of interstellar origin accelerated at the edge of the heliopause and accelerated at the termination shock in the solar wind, (3) high-energy particles of galactic origin far outside the heliosphere or the solar system, and (4) extragalactic sources. Cosmic radiation incident on the earth's atmosphere is classified into “primary” or “secondary” cosmic rays. Primary cosmic-ray particles include protons, helium nuclei, electrons, and nuclei of most elements of the periodic table of stellar origin. Nuclei of light elements such as lithium, beryllium, and boron are classified as secondary cosmic particles. The composition of cosmic radiation varies according to the 11-year solar cycle and the earth's magnetic latitude. Cosmic radiation consisting of high-energy nucleons striking the TOA collides with atoms of the air to produce a cascade of secondary subatomic particles and electromagnetic radiation referred to as showers of the cosmic radiation.