Slide 11 of 31
Notes:
The diagram shows the energy spectra of cosmic ray particles, sorted according to particle type.
The spectra are well-characterized as a power-law with a cut-off below about 1 GeV per nucleon (1e9 eV per nucleon). This cut-off is affected by solar activity - the fluxes of low energy particles decrease during periods of high solar activity, and increase when the Sun’s activity is low. The cut-off itself is due to the particles having to diffuse in towards the Earth from interstellar space through the outflowing solar wind. The effect is known as solar modulation.
The differential spectrum (at higher energies) can be written:
where x is in the range 2.5 to 2.7.
