Interpretation of the energy spectrum observed with the Telescope Array surface detectors

Abstract

The energy spectrum of cosmic rays above 10$^{18.2}$ eV is analyzed using Telescope Array (TA) surface detectors (SDs). The energy spectrum of cosmic rays above 10$^{17.2}$ eV is analyzed using TA fluorescence detector (TAFD) monocular mode. In this paper, the break point of the energy spectrum at around 10$^{18.7}$ eV which is known as ``ankle'' region is discussed using the data. We explored the possibility that cosmic ray protons from extra galactic sources can explain the feature of the spectrum shape in the ankle region. Magnetic fields in intergalactic space are also considered to discuss especially the low energy part of the data.