Does the "Knee" in Primary Cosmic Ray Spectrum Exist?

Abstract

The problem of the knee in primary cosmic ray at energy about 3–5 PeV is the most exciting problem in cosmic ray physics. Since 1958, physicists have been trying to solve this problem. In our opinion, the problem could be solved from the experimental point of view, whereas the primary spectrum would follow a pure power law. A key to the "knee" problem lies in the hadronic structure of EAS and its propagation in the Earth's atmosphere. Neither exotic processes nor new physics are used. An explanation of the approach and some results of Monte Carlo simulations are given below.

Remarks on astrophysical origin of the knee in the cosmic ray spectrum

“…Looking at Table 1 we can conclude that the measured data are more consistent with the prediction [2] shown in the last line than with the expectations made above under a supposition of the "knee" existence (first line). And finally: if the answer is negative then we probably have a natural universal theory of cosmic ray acceleration [1].…”

“…Up to date I incline to a negative answer to this question, because only in this case we could understand the experimental data. In the frame of the approach proposed in [2] there exists a natural explanation of the visible "disagreement" of the experimental data shown in Table 1: the "knee" does not exist in primary cosmic ray spectrum and should be observed only in electromagnetic component due to non-power law behaviour of the N e (E 0 ) in a region of ∼ 100 TeV/nucleon when hadron core reaches the sea level and coreless EAS's become coreful or normal ones. Muons and hadrons are almost insensitive to this critical point of the EAS development and follow a power law much better.…”

The knee in the cosmic ray energy spectrum from the simultaneous EAS charged particles and muon density spectra

“…Since α µ < α e , change in β µ should be larger than β e for a change in γ. Observationally, however, no significant change in β µ is found. This is why Stenkin objected the existence of a knee in the primary energy spectrum [8,9].…”

“…In other words the knee feature in the primary cosmic ray energy spectrum is not consistently revealed from electromagnetic, muonic and hadronic components of EAS. Stenkin proposed an alternative explanation of the break in shower size spectrum in terms of coreless EAS [8,9]. Further a new experiment PRISMA has been proposed to investigate the situation [10].…”

“…While arguing against the astrophysical knee, Stenkin did not consider any effect of change in primary mass composition in the knee region on air shower muon and electron spectra [8]. Here it is worthwhile to mention that the almost all the well known models of the knee generally predict for a change in the mass composition of cosmic rays across the knee energy.…”