Composition and Energetics

Cosmic rays, we now understand, mostly consist of relativistic protons, with an admixture of heavy elements and electrons. Their composition is, in fact, roughly solar, but with significant differences. An over-abundance of the light elements lithium, beryllium, and boron reflects the creation of secondary particles through nuclear reactions between the protons and the interstellar medium. These secondaries result from spallation, i. e., ejection from more massive target nuclei. More frequently, cosmic ray protons collide with the slow-moving protons of interstellar atomic hydrogen. Collision excites the target proton, causing it to emit a n° meson. The meson, in turn, decays into two 7-rays. This process accounts for much of the diffuse background of

1 The formulas we present are simplified, approximate versions of those found in the research literature. Quantitative rates are trustworthy to about a factor of two, under the conditions specified.

The Formation of Stars. Steven W. Stahler and Francesco Palla Copyright © 2004 Wiley-VCH Verlag GmbH & Co. KGaA, Weinheim ISBN: 3-527-40559-3

Table 7.1

Cloud Heating

Cloud Heating

Table 7.1

Process

Reaction

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