Models of the knee in the energy spectrum of cosmic rays

Abstract

The origin of the knee in the energy spectrum of cosmic rays is an outstanding problem in astroparticle physics. Numerous mechanisms have been proposed to explain the structure in the all-particle spectrum. In the article basic ideas of several models are summarized, including diffusive acceleration of cosmic rays in shock fronts, acceleration via cannonballs, leakage from the Galaxy, interactions with background particles in the interstellar medium, as well as new high-energy interactions in the atmosphere. The calculated energy spectra and mean logarithmic masses are compiled and compared to results from direct and indirect measurements.

Sensitivity of YAC to measure the light-component spectrum of primary cosmic rays at the ‘knee’ energies

“…Such structure of the all-particle energy spectrum is called the "knee", which is considered to be closely related to the origin, acceleration and propagation mechanism of cosmic rays. In order to explain the existence of the knee, many hypotheses and mechanisms [3,4] have been proposed. Although all these approaches can well describe the knee structure, there are much discrepancies in the prediction of the individual components at the knee region.…”

Are protons still dominant at the knee of the cosmic-ray energy spectrum?

“…In this case, the primary chemical composition is expected to become proton-enriched. There have been some calculations of the primary cosmic-ray energy spectrum based on various models on the origin of the knee [7], but all of them are still under debate due to lack of detailed knowledge about the chemical composition around the knee.…”

Mutually compensative pseudo solutions of primary energy spectra in the knee region

“…To decrease the contributions of the mutually compensative pseudo solutions one may apply a parameterization of the integral equations (1) [1,2,4,11,12] using a priori (expected from theories [17,18,19]) known primary energy spectra with a set of free spectral parameters. This transforms the EAS inverse problem into a set of equations with unknown spectral parameters, and thereby the EAS inverse problem is transmuted into a test of the given primary energy spectra using detected EAS data [4].…”