The Energy Spectrum of Cosmic Rays above 10$^{17.2}$ eV Measured by the Fluorescence Detectors of the Telescope Array Experiment in Seven Years

Abstract

The Telescope Array (TA) experiment is the largest detector to observe ultra-high-energy cosmic rays in the northern hemisphere. The fluorescence detectors at southern two stations of TA are newly constructed and have now completed seven years of steady operation. One advantage of monocular analysis of the fluorescence detectors is a lower energy threshold for cosmic rays than that of other techniques like stereoscopic observations or coincidences with the surface detector array, allowing the measurement of an energy spectrum covering three orders of magnitude in energy. Analyzing data collected during those seven years, we report the energy spectrum of cosmic rays covering a broad range of energies above 10$^{17.2}$ eV measured by the fluorescence detectors and a comparison with previously published results.