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Gamma Ray Showers Observed at Ground Level in Coincidence With Downward Lightning Leaders
Abbasi, R. U.,Abu‐,Zayyad, T.,Allen, M.,Barcikowski, E.,Belz, J. W.,Bergman, D. R.,Blake, S. A.,Byrne, M.,Cady, R.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Fujii, T.,Fukushima, M.,Furlich, G.,Goto, T. American Geophysical Union 2018 Journal of geophysical research. Atmospheres Vol.123 No.13
<P>Bursts of gamma ray showers have been observed in coincidence with downward propagating negative leaders in lightning flashes by the Telescope Array Surface Detector (TASD). The TASD is a 700-km(2) cosmic ray observatory located in southwestern Utah, USA. In data collected between 2014 and 2016, correlated observations showing the structure and temporal development of three shower-producing flashes were obtained with a 3-D lightning mapping array, and electric field change measurements were obtained for an additional seven flashes, in both cases colocated with the TASD. National Lightning Detection Network information was also used throughout. The showers arrived in a sequence of 2-5 short-duration (10s) bursts over time intervals of several hundred microseconds and originated at an altitude of similar or equal to 3-5km above ground level during the first 1-2ms of downward negative leader breakdown at the beginning of cloud-to-ground lightning flashes. The shower footprints, associated waveforms and the effect of atmospheric propagation indicate that the showers consist primarily of downward-beamed gamma radiation. This has been supported by GEANT simulation studies, which indicate primary source fluxes of similar or equal to 10(12)-10(14) photons for 16 degrees half-angle beams. We conclude that the showers are terrestrial gamma ray flashes, similar to those observed by satellites, but that the ground-based observations are more representative of the temporal source activity and are also more sensitive than satellite observations, which detect only the most powerful terrestrial gamma ray flashes.</P>
Mass composition of ultrahigh-energy cosmic rays with the Telescope Array Surface Detector data
Abbasi, R. U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Azuma, R.,Barcikowski, E.,Belz, J. W.,Bergman, D. R.,Blake, S. A.,Cady, R.,Cheon, B. G.,Chiba, J.,Chikawa, M.,di Matteo, A.,Fujii, T.,Fujita, K.,Fukushim American Physical Society 2019 Physical review. D Vol.99 No.2
The bursts of high energy events observed by the telescope array surface detector
Abbasi, R.U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Fujii, T.,Fukushima, M.,Goto, T.,Ha North-Holland 2017 Physics letters. Section A. Vol.381 No.32
The Telescope Array (TA) experiment is designed to detect air showers induced by ultra high energy cosmic rays. The TA ground Surface particle Detector (TASD) observed several short-time bursts of air shower like events. These bursts are not likely due to chance coincidence between single shower events. The expectation of chance coincidence is less than 10<SUP>-4</SUP> for five-year's observation. We checked the correlation between these bursts of events and lightning data, and found evidence for correlations in timing and position. Some features of the burst events are similar to those of a normal cosmic ray air shower, and some are not. On this paper, we report the observed bursts of air shower like events and their correlation with lightning.
SEARCH FOR ANISOTROPY OF ULTRAHIGH ENERGY COSMIC RAYS WITH THE TELESCOPE ARRAY EXPERIMENT
Abu-Zayyad, T.,Aida, R.,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J. W.,Bergman, D. R.,Blake, S. A.,Cady, R.,Cheon, B. G.,Chiba, J.,Chikawa, M.,Cho, E. J.,Cho, W. R.,Fujii, H.,Fujii, T.,F IOP Publishing 2012 The Astrophysical journal Vol.757 No.1
<P>We study the anisotropy of Ultra-High Energy Cosmic Ray (UHECR) events collected by the Telescope Array (TA) detector in the first 40 months of operation. Following earlier studies, we examine event sets with energy thresholds of 10 EeV, 40 EeV, and 57 EeV. We find that the distributions of the events in right ascension and declination are compatible with an isotropic distribution in all three sets. We then compare with previously reported clustering of the UHECR events at small angular scales. No significant clustering is found in the TA data. We then check the events with E > 57 EeV for correlations with nearby active galactic nuclei. No significant correlation is found. Finally, we examine all three sets for correlations with the large-scale structure (LSS) of the universe. We find that the two higher-energy sets are compatible with both an isotropic distribution and the hypothesis that UHECR sources follow the matter distribution of the universe (the LSS hypothesis), while the event set with E > 10 EeV is compatible with isotropy and is not compatible with the LSS hypothesis at 95% CL unless large deflection angles are also assumed. We show that accounting for UHECR deflections in a realistic model of the Galactic magnetic field can make this set compatible with the LSS hypothesis.</P>
Abu-Zayyad, T.,Aida, R.,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Cho, E.J.,Cho, W.R.,Fujii, H.,Fujii, T.,Fukuda, Elsevier 2015 Astroparticle physics Vol.61 No.-
<P><B>Abstract</B></P> <P>We measure the spectrum of cosmic rays with energies greater than <SUP> 10 18.2 </SUP> eV with the fluorescence detectors (FDs) and the surface detectors (SDs) of the Telescope Array Experiment using the data taken in our first 2.3-year observation from May 27, 2008 to September 7, 2010. A hybrid air shower reconstruction technique is employed to improve accuracies in determination of arrival directions and primary energies of cosmic rays using both FD and SD data. The energy spectrum presented here is in agreement with our previously published spectra and the HiRes results.</P>
Abbasi, R.U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Chae, M.J.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Cho, W.R.,Fujii, T.,Fuku Elsevier 2015 Astroparticle physics Vol.64 No.-
<P><B>Abstract</B></P> <P>Previous measurements of the composition of Ultra-High Energy Cosmic Rays (UHECRs) made by the High Resolution Fly’s Eye (HiRes) and Pierre Auger Observatory (PAO) are seemingly contradictory, but utilize different detection methods, as HiRes was a stereo detector and PAO is a hybrid detector. The five year Telescope Array (TA) Middle Drum hybrid composition measurement is similar in some, but not all, respects in methodology to PAO, and good agreement is evident between data and a light, largely protonic, composition when comparing the measurements to predictions obtained with the QGSJetII-03 and QGSJet-01c models. These models are also in agreement with previous HiRes stereo measurements, confirming the equivalence of the stereo and hybrid methods. The data is incompatible with a pure iron composition, for all models examined, over the available range of energies. The elongation rate and mean values of <SUB> X max </SUB> are in good agreement with Pierre Auger Observatory data. This analysis is presented using two methods: data cuts using simple geometrical variables and a new pattern recognition technique.</P>
Abu-Zayyad, T.,Aida, R.,Allen, M.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Cho, E.J.,Cho, W.R.,Fujii, H.,Fujii, T.,Fukuda, North-Holland ; Elsevier Science Ltd 2013 Astroparticle physics Vol.48 No.-
We present a measurement of the energy spectrum of ultra-high-energy cosmic rays performed by the Telescope Array experiment using monocular observations from its two new FADC-based fluorescence detectors. After a short description of the experiment, we describe the data analysis and event reconstruction procedures. Since the aperture of the experiment must be calculated by Monte Carlo simulation, we describe this calculation and the comparisons of simulated and real data used to verify the validity of the aperture calculation. Finally, we present the energy spectrum calculated from the merged monocular data sets of the two FADC-based detectors, and also the combination of this merged spectrum with an independent, previously published monocular spectrum measurement performed by Telescope Array's third fluorescence detector [T. Abu-Zayyad et al., The energy spectrum of Telescope Array's middle drum detector and the direct comparison to the high resolution fly's eye experiment, Astroparticle Physics 39 (2012) 109-119, http://dx.doi.org/10.1016/j.astropartphys.2012.05.012, Available from: <arXiv:1202.5141>]. This combined spectrum corroborates the recently published Telescope Array surface detector spectrum [T. Abu-Zayyad, et al., The cosmic-ray energy spectrum observed with the surface detector of the Telescope Array experiment, ApJ 768 (2013) L1, http://dx.doi.org/10.1088/2041-8205/768/1/L1, Available from: <arXiv:1205.5067>] with independent systematic uncertainties.
Abbasi, R.U.,Abe, M.,Abu-Zayyad, T.,Allen, M.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Cho, W.R.,Fujii, T.,Fukushima, M.,Goto, T.,Hanlo North-Holland 2016 Astroparticle physics Vol.80 No.-
<P>The Telescope Array (TA) experiment is the largest detector to observe ultra-high-energy cosmic rays in the northern hemisphere. The fluorescence detectors at 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. (C) 2016 Elsevier B.V. All rights reserved.</P>
The hybrid energy spectrum of Telescope Array's Middle Drum Detector and surface array
Abbasi, R.U.,Abe, M.,Abu-Zayyad, T.,Allen, M.G.,Anderson, R.,Azuma, R.,Barcikowski, E.,Belz, J.W.,Bergman, D.R.,Blake, S.A.,Cady, R.,Chae, M.J.,Cheon, B.G.,Chiba, J.,Chikawa, M.,Cho, W.R.,Fujii, T.,Fu North-Holland ; Elsevier Science Ltd 2015 Astroparticle physics Vol.68 No.-
The Telescope Array experiment studies ultra high energy cosmic rays using a hybrid detector. Fluorescence telescopes measure the longitudinal development of the extensive air shower generated when a primary cosmic ray particle interacts with the atmosphere. Meanwhile, scintillator detectors measure the lateral distribution of secondary shower particles that hit the ground. The Middle Drum (MD) fluorescence telescope station consists of 14 telescopes from the High Resolution Fly's Eye (HiRes) experiment, providing a direct link back to the HiRes measurements. Using the scintillator detector data in conjunction with the telescope data improves the geometrical reconstruction of the showers significantly, and hence, provides a more accurate reconstruction of the energy of the primary particle. The Middle Drum hybrid spectrum is presented and compared to that measured by the Middle Drum station in monocular mode. Further, the hybrid data establishes a link between the Middle Drum data and the surface array. A comparison between the Middle Drum hybrid energy spectrum and scintillator Surface Detector (SD) spectrum is also shown.