The Telescope Array (TA), deployed in the desert of central Utah, is the largest cosmic ray detector in the Northern hemisphere. It was initially designed to observe ultra high energy cosmic rays with energies > 10^{19} eV. It consists of three telescope stations viewing the sky over an array of scintillator surface detectors. The fluorescence telescopes observe the longitudinal development of an extensive air shower induced by an incident cosmic ray by detecting the scintillation light as the shower develops. Meanwhile, the array of scintillator surface detectors measures the lateral distribution of particles reaching the Earth's surface. More recently the Telescope Array Low-energy Extension (TALE) was added to lower the experiment'senergy threshold. This was accomplished by installing high elevation angle telescopes to one of the telescope stations and adding a graded array of more densely spaced surface detectors to the existing main array. This allows us to extend our study to cosmic rays as low in energy as ~10^{15.3} eV. The observatory now consists of 48 fluorescence telescopes at three stations viewing the sky above an array of 610 surface detectors. The scintillator array is spread over ~750 km^{2}. One complication of combining TA and TALE telescope data is that these telescopes use significantly different electronics for historical reasons. In this talk, I will present a measurement of the energy spectrum in the energy range of 10^{17.2}-10^{19.0} eV using fluorescence data collected by the TA and TALE telescopes.
JiHee Kim earned her B.S. and a M.S. degree in Astronomy from Chungnam National University in South Korea. During this time she was also working with the Telescope Array which is an international cosmic ray research collaboration. She moved to the University of Utah, the host institution of the experiment, to pursue her Ph.D. which she completed in 2018. Dr. Kim is currently a post-doctoral research associate at the University of Utah where she is continuing research on the energy spectrum and composition of ultra high energy cosmic rays at the Telescope Array as well as studying the systematic uncertainty in air fluorescence yields.