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RISS 인기검색어
- 검색키워드
- 저자 : Kenny Ng (검색결과 3 건)
- 무료
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- 유료
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First observation of time variation in the solar-disk gamma-ray flux with Fermi
Ng, Kenny C. Y.,Beacom, John F.,Peter, Annika H. G.,Rott, Carsten American Physical Society 2016 Physical Review D Vol.94 No.2
<P>The solar disk is a bright gamma-ray source. Surprisingly, its flux is about 1 order of magnitude higher than predicted. As a first step toward understanding the physical origin of this discrepancy, we perform a new analysis in 1-100 GeV using 6 years of public Fermi-LAT data. Compared to the previous analysis by the Fermi Collaboration, which analyzed 1.5 years of data and detected the solar disk in 0.1-10 GeV, we find two new and significant results: (1) In the 1-10 GeV flux (detected at > 5 sigma), we discover a significant time variation that anticorrelates with solar activity, and (2) we detect gamma rays in 10-30 GeV at > 5 sigma and in 30-100 GeV at > 2 sigma. The time variation strongly indicates that solar-disk gamma rays are induced by cosmic rays and that solar atmospheric magnetic fields play an important role. Our results provide essential clues for understanding the underlying gamma-ray production processes, which may allow new probes of solar atmospheric magnetic fields, cosmic rays in the solar system, and possible new physics. Finally, we show that the Sun is a promising new target for ground-based TeV gamma-ray telescopes such as HAWC and LHAASO.</P>
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Solar atmospheric neutrinos: A new neutrino floor for dark matter searches
Ng, Kenny C. Y.,Beacom, John F.,Peter, Annika H. G.,Rott, Carsten American Physical Society 2017 Physical Review D Vol.96 No.10
<P>As is well known, dark matter direct detection experiments will ultimately be limited by a 'neutrino floor,' due to the scattering of nuclei by MeV neutrinos from, e.g., nuclear fusion in the Sun. Here we point out the existence of a new neutrino floor that will similarly limit indirect detection with the Sun, due to high-energy neutrinos from cosmic-ray interactions with the solar atmosphere. We have two key findings. First, solar atmospheric neutrinos. greater than or similar to 1 TeV cause a sensitivity floor for standard weakly interacting massive particles (WIMP) scenarios, for which higher-energy neutrinos are absorbed in the Sun. This floor will be reached once the present sensitivity is improved by just 1 order of magnitude. Second, for neutrinos. 1 TeV, which can be isolated by muon energy loss rate, solar atmospheric neutrinos should soon be detectable in IceCube. Discovery will help probe the complicated effects of solar magnetic fields on cosmic rays. These events will be backgrounds to WIMP scenarios with long-lived mediators, for which higher-energy neutrinos can escape from the Sun.</P>
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