• Title/Summary/Keyword: ultra high energy cosmic rays

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Influence of the Galactic Magnetic Field on the Distribution of Ultra-high-Energy Cosmic Rays

  • Kim, Jihyun;Kim, Hang Bae;Ryu, Dongsu
    • The Bulletin of The Korean Astronomical Society
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    • v.40 no.2
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    • pp.38.3-38.3
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    • 2015

  • Recently, the Pierre Auger Observatory (PAO), the largest ground-based project for detecting ultra-high-energy cosmic rays (UHECRs), published their 10-year data. We can access an unprecedented number of UHECR data observed by the project, which give us a possibility to get an accurate statistical test result. In this work, we investigate the influence of the galactic magnetic field (GMF) on the distribution of UHECRs by searching the correlation with the large-scale structure (LSS) of the universe. We simulate the mock UHECR events whose trajectories from the sources would be deflected by the Gaussian smearing angle which reflects the influence by the GMF. By the statistical test, we compare the correlation between the expected/observed distribution of UHECRs and the LSS of the universe in the regions of sky divided by the galactic latitude, varying the smearing angle. Here, we assume the deflections by the GMF are mainly dependent on the galactic latitude. Using the maximum likelihood estimation, we find the best-fit smearing angle in each region. If we get a trend that best-fit smearing angles differ from each region, the influence of GMF may be stronger than that of intergalactic magnetic fields (IGMF) because it is known that the distribution of IGMF follows the LSS of the universe. Also, we can estimate the strength of the GMF using the best-fit parameter by the maximum likelihood.

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Heavy ion fragment beam test of Silicon Charge Detector

  • Kim, Mi-Yeong;Nam, Sin-U;Park, Na-Hui;Park, Il-Hong;Bok, Jeong-Beom;Yang, Jong-Man;Lee, Jae-Geum;Han, Ji-Hye;Hyeon, Hyo-Jeong
    • Bulletin of the Korean Space Science Society
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    • 2004.04a
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    • pp.100-100
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    • 2004

  • Silicon Charge Detector is to measure the charge of incident cosmic-ray nuclei with a resolution of 0.2 charge unit for atomic number, Z=1-30 with energy range from 1 to 1000 TeV. It is one of detectors for CREAM (Cosmic Ray Energetics And Mass) experiment to test current models of source and acceleration mechanisms of ultra high energy cosmic rays. It's first flight will be with a NASA zero pressure balloon planned to be launched from McMurdo Station, Antarctica in December 2004. (omitted)

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Intergalactic Magnetic Field and Arrival Direction of Ultra-High-Energy Iron Nuclei

  • Ryu, Dongsu;Kang, Hyesung;Das, Santabrata
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.2
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    • pp.78.2-78.2
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    • 2012

  • We have studied how the intergalactic magnetic field (IGMF) affects the propagation of super-GZK iron nuclei that originate from extragalactic sources within the local GZK sphere. Toward this end, we set up hypothetical sources of ultra-high-energy cosmic-rays (UHECRs), virtual observers, and the magnetized cosmic web in a model universe constructed from cosmological structure formation simulations. We then arranged a set of reference objects at high density region to represent astronomical objects formed in the large scale structure (LSS). With our model IGMF, the paths of UHE iron nuclei are deflected on average by about 70 degrees, which might indicate a nearly isotropic distribution of arrival directions. However, the separation angle between the arrival directions and the nearest reference object on the LSS is only ~6 degrees, which is twice the mean distance to the nearest neighbors among the reference objects. This means that the positional correlation of observed UHE iron events with their true sources would be erased by the IGMF, but the correlation with the LSS itself is to be sustained. We discuss implications of our findings for correlations studies of real UHECR events.

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Deflection of Ultra-high Energy Cosmic Rays by the Galactic Magnetic Field

  • Kim, Jihyun;Kim, Hang Bae;Ryu, Dongsu
    • The Bulletin of The Korean Astronomical Society
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    • v.39 no.2
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    • pp.73.1-73.1
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    • 2014

  • We investigate the influence of the galactic magnetic field (GMF) on the arrival direction (AD) of ultra-high energy cosmic rays (UHECRs) by searching the correlation with the large-scale structure (LSS) of the universe. The deflection angle of UHECRs from sources by the GMF is reflected in a source model by introducing the Gaussian smearing angle as a free parameter. Assuming the deflections by the GMF are mainly dependent on the galactic latitude, b, we divide the regions of sky by b and analyze the correlation between the AD of UHECRs and the LSS of the universe in each region varying the smearing angle. We find the deflection is strongly dependent on the galactic latitude by the maximum likelihood estimation. Specifically, the best-fit smearing angles are $9^{\circ}$ and $84^{\circ}$ in the high galactic latitude (HGL), $-90^{\circ}$ < b < $-60^{\circ}$, and in the low galactic latitude (LGL), $-30^{\circ}$ < b < $30^{\circ}$, respectively. The strength of GMF becomes stronger from the HGL to the LGL. From the results, we can estimate the strength of GMF in each region. In the LGL, for example, if we assume UHECRs are protons, we have the order of $100{\mu}G$ GMF, which is much stronger than the expected value of conventional GMF model. However, if the primaries are heavy nuclei, which is consistent with the observational result of mass composition analysis, the order of GMF strength is a few ${\mu}G$. More data from the future experiments make it possible to study the GMF between the source of UHECRs and Earth more accurately.

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FR-II radio jets and the acceleration of UHECRs

  • Seo, Jeongbhin;Kang, Hyesung;Ryu, Dongsu
    • The Bulletin of The Korean Astronomical Society
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    • v.46 no.2
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    • pp.39.2-39.2
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    • 2021

  • To investigate the acceleration of ultra-high energy cosmic rays (UHECRs) in relativistic jets of FR-II galaxies, we simulate high-power jets with jet powers of Q~10^46erg/s in a stratified galaxy cluster halo using a state-of-art relativistic hydrodynamic (RHD) code we have recently developed. With the simulated jet-induced flow profiles, we then perform Monte-Carlo simulations, where the transport of high-energy particles is followed assuming large-angle scatterings in the flow-rest frame. We estimate the energy gains and acceleration times in the acceleration processes by shocks, shear, and turbulence. We present the results and discuss implications on the acceleration of UHECRs in FR II radio jets.

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A comparison study of CORSIKA and COSMOS simulations for extensive air showers

  • Kim, Ji-Hee;Roh, Soon-Young;Ryu, Dong-Su;Kang, Hye-Sung
    • The Bulletin of The Korean Astronomical Society
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    • v.37 no.1
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    • pp.69.1-69.1
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    • 2012

  • Monte Carlo codes for extensive air shower (EAS) simulate the development of EASs initiated in the Earth's atmosphere by ultra-high energy cosmic rays (UHECRs) with energy exceeding - $10^{18}$ eV. Here, we compare EAS simulations with two different codes, CORSIKA and COSMOS, presenting quantities including the longitudinal distribution of particles, depth of shower maximum, kinetic energy distribution of particle at the ground, and calorimetric energy. In addition, the lateral distribution of local energy density far from the EAS core has been known as an important quantity to estimate the energy of UHECRs. We also present the lateral distribution function obtained from GEANT4 simulations for detector response.

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