Evidence for an intermediate-scale energy spectrum anisotropy has been found in the arrival directions of ultra-high energy cosmic rays for energies greater than 1019.2 eV in the northern hemisphere ...using 7 years of Telescope Array surface detector data. A relative energy distribution test is done comparing events inside oversampled spherical caps of equal exposure, to those outside, using the Poisson likelihood ratio. The center of maximum significance is at 9h16m, 45°, and has a deficit of events with energies 1019.2 ≤ E < 1019.75 eV and an excess for E ≥ 1019.75 eV. The post-trial probability of this energy anisotropy, appearing by chance anywhere on an isotropic sky, is found by Monte Carlo simulation to be 9 × 10−5 (3.74 global).
It was proposed that the two phenomena, WMAP-Planck haze and Fermi bubbles, may have a common origin. In the present paper we analyze the spatial structure of the haze using the Planck 2018 data ...release. It is found that the spatial dimensions and locations of WMAP-Planck haze and Fermi bubbles are compatible within the experimental uncertainties. No substructures similar to the Fermi bubbles cocoon are identified in the Planck data. Comparison with the spatial extent of possible synchrotron emission caused by the electron-positron pair emitted by the Galactic center pulsar population and by the decay of dark matter particles in the Galactic center region are performed. Both galactic pulsars and dark matter decay remain viable explanations of the WMAP-Planck haze.
We use a new method to estimate the injected mass composition of ultrahigh cosmic rays (UHECRs) at energies higher than 10 EeV. The method is based on comparison of the energy-dependent distribution ...of cosmic ray arrival directions as measured by the Telescope Array experiment (TA) with that calculated in a given putative model of UHECR under the assumption that sources trace the large-scale structure (LSS) of the Universe. As we report in the companion letter, the TA data show large deflections with respect to the LSS which can be explained, assuming small extra-galactic magnetic fields (EGMF), by an intermediate composition changing to a heavy one (iron) in the highest energy bin. Here we show that these results are robust to uncertainties in UHECR injection spectra, the energy scale of the experiment and galactic magnetic fields (GMF). The assumption of weak EGMF, however, strongly affects this interpretation at all but the highest energies E > 100 EeV, where the remarkable isotropy of the data implies a heavy injected composition even in the case of strong EGMF. This result also holds if UHECR sources are as rare as \(2 \times 10^{-5}\) Mpc\(^{-3}\), that is the conservative lower limit for the source number density.
We report an estimation of the injected mass composition of ultra-high energy
cosmic rays (UHECRs) at energies higher than 10 EeV. The composition is
inferred from an energy-dependent sky ...distribution of UHECR events observed by
the Telescope Array surface detector by comparing it to the Large Scale
Structure of the local Universe. In the case of negligible extra-galactic
magnetic fields the results are consistent with a relatively heavy injected
composition at E ~ 10 EeV that becomes lighter up to E ~ 100 EeV, while the
composition at E > 100 EeV is very heavy. The latter is true even in the
presence of highest experimentally allowed extra-galactic magnetic fields,
while the composition at lower energies can be light if a strong EGMF is
present. The effect of the uncertainty in the galactic magnetic field on these
results is subdominant.
We report on an observation of the difference between northern and southern skies of the ultrahigh energy cosmic ray energy spectrum with a significance of \({\sim}8\sigma\). We use measurements from ...the two largest experiments\(\unicode{x2014}\)the Telescope Array observing the northern hemisphere and the Pierre Auger Observatory viewing the southern hemisphere. Since the comparison of two measurements from different observatories introduces the issue of possible systematic differences between detectors and analyses, we validate the methodology of the comparison by examining the region of the sky where the apertures of the two observatories overlap. Although the spectra differ in this region, we find that there is only a \(1.8\sigma\) difference between the spectrum measurements when anisotropic regions are removed and a fiducial cut in the aperture is applied.
In this paper, we present the first high-speed video observation of a cloud-to-ground lightning flash and its associated downward-directed Terrestrial Gamma-ray Flash (TGF). The optical emission of ...the event was observed by a high-speed video camera running at 40,000 frames per second in conjunction with the Telescope Array Surface Detector, Lightning Mapping Array, interferometer, electric-field fast antenna, and the National Lightning Detection Network. The cloud-to-ground flash associated with the observed TGF was formed by a fast downward leader followed by a very intense return stroke peak current of -154 kA. The TGF occurred while the downward leader was below cloud base, and even when it was halfway in its propagation to ground. The suite of gamma-ray and lightning instruments, timing resolution, and source proximity offer us detailed information and therefore a unique look at the TGF phenomena.
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