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Shaping FEL radiation
Primož Rebernik Ribič, 2016, published scientific conference contribution abstract (invited lecture)

Found in: ključnih besedah
Keywords: radiation, synchrotron, free-electron laser
Published: 16.01.2020; Views: 775; Downloads: 3
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14.
Search for Anisotropy in the Ultra High Energy Cosmic Ray Spectrum using the Telescope Array Surface Detector
J. P. Lundquist, R.U. Abbasi, 2017, other component parts

Abstract: The Telescope Array (TA) experiment is located in the western desert of Utah, USA, and observes ultra high energy cosmic rays (UHECRs) in the Northern hemisphere. At the highest energies, E>10~EeV, the shape of cosmic ray energy spectrum may carry an imprint of the source density distribution along the line of sight different in different directions of the sky. In this study, we search for such directional variations in the shape of the energy spectrum using events observed with the Telescope Array's surface detector. We divide the TA field of view into two nearly equal-exposure regions: the "on-source" region which we define as ±30∘ of the supergalactic plane containing mostly nearby structures, and the complementary "off-source" region where the sources are further away on average. We compare the UHECR spectra in these regions by fitting them to the broken power law and comparing the resulting parameters. We find that the off-source spectrum has an earlier break at highest energies. The chance probability to obtain such or larger difference in statistically equivalent distributions is estimated as 6.2±1.1×10−4 (3.2σ) by a Monte-Carlo simulation. The observed difference in spectra is in a reasonable quantitative agreement with a simplified model that assumes that the UHECR sources trace the galaxy distribution from the 2MRS catalogue, primary particles are protons and the magnetic deflections can be neglected.
Found in: ključnih besedah
Summary of found: ...cosmic radiation: UHE, detector: surface, cosmic radiation: spectrum, cosmic...
Keywords: cosmic radiation: UHE, detector: surface, cosmic radiation: spectrum, cosmic radiation: energy spectrum, deflection: magnetic, numerical calculations: Monte Carlo, anisotropy
Published: 27.04.2020; Views: 683; Downloads: 27
.pdf Fulltext (169,05 KB)

15.
TA Anisotropy Summary
J. P. Lundquist, K. Kawata, 2019, published scientific conference contribution

Abstract: The Telescope Array (TA) is the largest ultra-high-energy cosmic-ray (UHECR) detector in the northern hemisphere. It consists of an array of 507 surface detectors (SD) covering a total 700 km^2 and three fluorescence detector stations overlooking the SD array. In this proceedings, we summarize recent results on the search for directional anisotropy of UHECRs using the latest dataset collected by the TA SD array. We obtained hints of the anisotropy of the UHECRs in the northern sky from the various analyses.
Found in: ključnih besedah
Summary of found: ...cosmic radiation, UHE detector, fluorescence detector, surface,Telescope Array Experiment,...
Keywords: cosmic radiation, UHE detector, fluorescence detector, surface, Telescope Array Experiment, anisotropy, experimental results
Published: 28.04.2020; Views: 697; Downloads: 25
.pdf Fulltext (1,88 MB)

16.
The bursts of high energy events observed by the telescope array surface detector
J. P. Lundquist, R.U. Abbasi, 2017, original scientific article

Abstract: 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^-4 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.
Found in: ključnih besedah
Summary of found: ...High energy radiation, Lightning, Terrestrial gamma-ray flash...
Keywords: High energy radiation, Lightning, Terrestrial gamma-ray flash
Published: 30.04.2020; Views: 717; Downloads: 0
.pdf Fulltext (1,70 MB)

17.
Impact of bacterial ice nucleating particles on weather predicted by a numerical weather prediction model
Maher Sahyoun, Ulrik S. Korsholm, Jens H. Sørensen, Tina Šantl Temkiv, Kai Finster, Ulrich Gosewinkel, Niels Woetmann Nielsen, 2017, original scientific article

Found in: ključnih besedah
Summary of found: ...neous ice nucleation, Bacterial INP, Cloud ice, Precipitation, Global solar radiation, Numerical weather prediction model...
Keywords: Heterogeneous ice nucleation, Bacterial INP, Cloud ice, Precipitation, Global solar radiation, Numerical weather prediction model
Published: 04.01.2021; Views: 309; Downloads: 0
.pdf Fulltext (4,40 MB)

18.
Evidence for a supergalactic structure of magnetic deflection multiplets of ultra-high-energy cosmic rays
R. U. Abbasi, T. Abu-Zayyad, Mitsuhiro Abe, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, D. R. Bergman, S. A. Blake, Jon Paul Lundquist, 2020, original scientific article

Abstract: Evidence for a large-scale supergalactic cosmic-ray multiplet (arrival directions correlated with energy) structure is reported for ultra-high-energy cosmic-ray (UHECR) energies above 1019 eV using 7 years of data from the Telescope Array (TA) surface detector and updated to 10 years. Previous energy–position correlation studies have made assumptions regarding magnetic field shapes and strength, and UHECR composition. Here the assumption tested is that, because the supergalactic plane is a fit to the average matter density of the local large-scale structure, UHECR sources and intervening extragalactic magnetic fields are correlated with this plane. This supergalactic deflection hypothesis is tested by the entire field-of-view (FOV) behavior of the strength of intermediate-scale energy–angle correlations. These multiplets are measured in spherical cap section bins (wedges) of the FOV to account for coherent and random magnetic fields. The structure found is consistent with supergalactic deflection, the previously published energy spectrum anisotropy results of the TA (the Hotspot and Coldspot), and toy-model simulations of a supergalactic magnetic sheet. The seven year data posttrial significance of this supergalactic structure of multiplets appearing by chance, on an isotropic sky, is found by Monte Carlo simulation to be 4.2σ. The 10 years of data posttrial significance is 4.1σ. Furthermore, the starburst galaxy M82 is shown to be a possible source of the TA Hotspot, and an estimate of the supergalactic magnetic field using UHECR measurements is presented.
Found in: ključnih besedah
Summary of found: ...extragalactic magnetic fields, ultra-high-energy cosmic radiation, cosmic rays, high energy astrophysics, astrophysical magnetism,...
Keywords: extragalactic magnetic fields, ultra-high-energy cosmic radiation, cosmic rays, high energy astrophysics, astrophysical magnetism, cosmic ray astronomy, cosmic ray sources
Published: 05.02.2021; Views: 259; Downloads: 9
URL Fulltext (0,00 KB)
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19.
Search for large-scale anisotropy on arrival directions of ultra-high-energy cosmic rays observed with the telescope array experiment
Mitsuhiro Abe, R. U. Abbasi, T. Abu-Zayyad, M. Allen, R. Azuma, E. Barcikowski, J. W. Belz, D. R. Bergman, S. A. Blake, Jon Paul Lundquist, 2020, original scientific article

Abstract: Motivated by the detection of a significant dipole structure in the arrival directions of ultra-high-energy cosmic rays above 8 EeV reported by the Pierre Auger Observatory (Auger), we search for a large-scale anisotropy using data collected with the surface detector array of the Telescope Array Experiment (TA). With 11 yr of TA data, a dipole structure in a projection of the R.A. is fitted with an amplitude of 3.3% ± 1.9% and a phase of 131° ± 33°. The corresponding 99% confidence-level upper limit on the amplitude is 7.3%. At the current level of statistics, the fitted result is compatible with both an isotropic distribution and the dipole structure reported by Auger.
Found in: ključnih besedah
Summary of found: ...cosmic rays, ultra-high-energy cosmic radiation, cosmic ray sources, cosmic ray showers, cosmic...
Keywords: cosmic rays, ultra-high-energy cosmic radiation, cosmic ray sources, cosmic ray showers, cosmic ray detectors, cosmic ray astronomy, extragalactic astronomy
Published: 05.02.2021; Views: 250; Downloads: 0
.pdf Fulltext (548,15 KB)

20.
Scrutinizing FR 0 radio galaxies as ultra-high-energy cosmic ray source candidates
Anita Reimer, Lukas Merten, Margot Boughelilba, Paolo Da Vela, Serguei Vorobiov, Fabrizio Tavecchio, Giacomo Bonnoli, Jon Paul Lundquist, Chiara Righi, 2021, original scientific article

Abstract: Fanaroff-Riley (FR) 0 radio galaxies compose a new class of radio galaxies, which are usually weaker but much more numerous than the well-established class of FR 1 and FR 2 galaxies. The latter classes have been proposed as sources of the ultra-high-energy cosmic rays (UHECRs) with energies reaching up to eV. Based on this conjecture, the possibility of UHECR acceleration and survival in an FR 0 source environment is examined in this work. In doing so, an average spectral energy distribution (SED) based on data from the FR 0 catalog (FR0CAT) is compiled. The resulting photon fields are used as targets for UHECRs, which suffer from electromagnetic pair production, photo-disintegration, photo-meson production losses, and synchrotron radiation. Multiple mechanisms are discussed to assess the UHECR acceleration probability, including Fermi-I order and gradual shear accelerations, and particle escape from the source region. This work shows that in a hybrid scenario, combining Fermi and shear accelerations, FR 0 galaxies can contribute to the observed UHECR flux, as long as where shear acceleration starts to dominate over escape. Even in less optimistic scenarios, FR 0s can be expected to contribute to the cosmic-ray flux between the knee and the ankle. Our results are relatively robust with respect to the realized magnetic turbulence model and the speed of the accelerating shocks.
Found in: ključnih besedah
Summary of found: ...roduction, photo-disintegration, photo-meson production losses, and synchrotron radiation. Multiple mechanisms are discussed to assess the...
Keywords: acceleration of particles, nonthermal radiation mechanisms, jets, active galaxies, cosmic rays
Published: 05.02.2021; Views: 327; Downloads: 0
.pdf Fulltext (4,15 MB)
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