Fig4_2 Particle Flux vs Particle Energy

Fig4_2 Particle Flux vs Particle Energy

Fig. 4.2 . The energy spectrum of cosmic ray particles striking the outer atmosphere of the Earth. The particle flux is plotted as a function of the particle energy in units of electron volts, abbreviated eV, where 1 eV = 1.602 x 10-19 J and 1 GeV = 109 eV, or a billion eV. The most abundant cosmic ray particles are protons with energies of about 1.5 billion eV, and every second about 640 of them enter every square meter of the Earth’s outer atmosphere. They are probably accelerated to high energy during the supernova explosions of massive stars. One cosmic ray proton of 10 billion eV in energy enters each square meter of the Earth’s outer atmosphere every second; the more energetic cosmic ray particles of a hundred thousand million eV are less abundant, with one per square meter every year. Solar flares can emit protons with energies of 10 billion eV or less, and these solar energetic particles can strike the Earth when the solar active region is on the near side of the Sun. Cosmic rays with low flux and very high energy, greater than a million billion eV may be of extragalactic origin.

Copyright 2010, Professor Kenneth R. Lang, Tufts University