Slide 27 of 31
Notes:
We are now going to examine electrons as sources of cosmic rays.
An important factor is that the mass of an electron is much smaller than that of a proton, therefore they lose their energy much more rapidly than the heavier particles.
One major consequence of their shorter lifetime is that we can deduce that sources of electron cosmic rays are Galactic (they would have lost their energy by the time they reached us otherwise).
The observed energy density in cosmic ray electrons is 4,000 eV/m^3, much smaller than that of the total cosmic ray energy density.
