The Cosmic Ray Energy Spectrum between 2 PeV and 2 EeV Observed with the TALE Detector in Monocular Mode

Abstract

We report on a measurement of the cosmic ray composition by the Telescope Array Low-Energy Extension (TALE) air fluorescence detector (FD). By making use of the Cherenkov light signal in addition to air fluorescence light from cosmic ray (CR) induced extensive air showers, the TALE FD can measure the properties of the cosmic rays with energies as low as ∼ 2 PeV and exceeding 1 EeV. In this paper, we present results on the measurement of X max distributions of showers observed over this energy range. Data collected over a period of ∼ 4 years was analyzed for this study. The resulting X max distributions are compared to the Monte Carlo (MC) simulated data distributions for primary cosmic rays with varying composition and a 4-component fit is performed. The comparison and fit are performed for energy bins, of width 0.1 or 0.2 in log 10 (E/eV), spanning the full range of the measured energies. We also examine the mean X max value as a function of energy for cosmic rays with energies greater than 10 15.8 eV. Below 10 17.3 eV, the slope of the mean X max as a function of energy (the elongation rate) for the data is significantly smaller than that of all elements in the models, indicating that the composition is becoming heavier with energy in this energy range. This is consistent with a rigidity-dependent cutoff of events from galactic sources. Finally, an increase in the X max elongation rate is observed at energies just above 10 17 eV indicating another change in the cosmic rays composition.

Cosmic ray models

“…The spectrum can be approximated by a multiply broken power-law, with a first break at 200 GeV as discussed in the previous section. At the energy E k 4 PeV, a second pronounced change dubbed the CR knee occurs where the spectral Figure 22: The all-particle CR spectrum multiplied with E 3 as function of energy together with experimental data from ATIC-2 [271], TUNKA [272], TUNKA-HiSCORE [273], IceTop [274], TALE [275], the PAO [276], and the TA [277]. All data are consistent after a 10% energy shift, i.e.…”

Cosmic rays escaping from Galactic starburst-driven superbubbles

“…The red, round and blue, square data points are hydrogen and helium nuclei components of CRs above the knee from KASCADE-Grande (Apel et al 2013). Rest of the shown data are taken from AKENO, 1992, All: Nagano et al (1992; EAS-TOP, 1999, All: Aglietta et al (1999); HiRes-II, 2008, All: Abbasi et al (2008); Tibet-III, 2008, All: Amenomori et al (2008);Yakutsk, 2009, All: Ivanov, Knurenko, & Sleptsov (2009KASCADE, 2011: Finger (2011; GAMMA, 2014, All: Ter-Antonyan (2014); AUGER, 2017, All: Fenu et al (2017); TALE, 2018, All: Abbasi et al (2018). applying our model, M gas is the total gas mass contained inside the CR halo, estimated to be 1.0×10 10 M , and X esc is the grammage along the CR path length, which is obtained via observations on the ratio of boron to carbon fluxes (e.g. Adriani et al 2014;Aguilar et al 2016).…”

Fifty Years of Energy Extraction from Rotating Black Hole: Revisiting Magnetic Penrose Process

“…Surprisingly, this energy has the same order of magnitude as the knee of the cosmic ray energy spectra, above which flux of particles demonstrate significant suppression [94]. Although many models have been suggested, the explanation of the origin of knee is still in strong debate due to number of uncertainties in Galactic magnetic field structure and lack of direct detections of primary cosmic rays.…”