Browsing by Autor "T. Sako"

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ALPACA air shower array to explore 100TeV gamma-ray sky in Bolivia
(2019) T. Sako; Carlos I. Calle; K. Hibino; N. Hotta; Y. Katayose; C. Kato; Shin‐ichiro Kato; K. Kawata; W. Kihara; Y. Ko
Andes Large area PArticle detector for Cosmic ray physics and Astronomy (ALPACA) is a new air shower array project as a collaboration between Bolivia and Japan to explore the 100 TeV gamma-ray sky in the southern hemisphere. In a plateau near the Chacaltaya mountain at 4,740 m altitude, a surface detector array covering 82,800 m$^{2}$ with underground water Cherenkov muon detectors of total 5,400 m$^{2}$ area will be constructed. Because of 2 m soil overburden, the muon detectors can detect muons of >1.2 GeV in air showers with a high purity. Using the conventional surface array to determine the primary energy and the arrival direction, the underground muon detectors improve the gamma/hadron separation and also mass identification of primary cosmic rays. For gamma-ray showers within zenith angle of 45 degrees, ALPACA has a full effective area above 20TeV. At 20 TeV and 100 TeV, 99% and 99.9% hadron showers are rejected, respectively, while keeping the gamma-ray detection efficiency above 90%. Many interesting galactic objects can be observed with 0.2 degree angular resolution at 100 TeV with >2,000 hours/year exposure. ALPACA enables us the first sensitive survey of the southern gamma-ray sky at 100 TeV energy range that is crucial to identify PeV accelerating objects. Preparation for infrastructure and con- struction of a pathfinder array ALPAQUITA are ongoing. Scientific targets, expected performance of ALPACA including the prospects for some CR observations and current status are described.
ALPACA experiment: A new air shower array to explore the sub-PeV gamma-ray sky in the southern hemisphere
(2022) T. Sako; M. Anzorena; A. Gomi; Y. Hayashi; K. Hibino; N. Hotta; A Jimenez-Meza; Y. Katayose; C. Kato; S. Kato
In the last few years, gamma-ray astronomy opens a new window in the sub-PeV to PeV range inaugurated by the Tibet AS𝛾 collaboration followed by the HAWC and LHAASO collaborations. The successful three experiments are located in the northern hemisphere and they are not able to study the southern sky where potential interesting objects are known to exist. Andes Large area PArticle detector for Cosmic ray physics and Astronomy (ALPACA) is a project to cover the southern sub-PeV to PeV sky using a new air shower array at the plateau of the Chacaltaya mountain at the altitude of 4,740 m in Bolivia. The prime target of ALPACA is to reveal PeV cosmic-ray accelerators presumably existing in the galactic plane, including the galactic center. A prototype array ALPAQUITA consisting of 97 surface counters and 900 m$^2$ muon detectors is now under construction and planned to partly start data taking in 2022. The extension to the 401 counters and 3,700 m$^2$ muon detectors is scheduled in 2024. In this contribution, a general introduction to ALPACA, the current status of ALPAQUITA, and an extension plan after 2023 are presented.
Detection of high-energy solar neutrons and protons by ground level detectors on April 15, 2001
(Elsevier BV, 2008) Y. Muraki; Y. Matsubara; S. Masuda; S. Sakakibara; T. Sako; K. Watanabe; R. Bütikofer; E. O. Flückiger; A. Chilingarian; G. Hovsepyan
Detection of Solar Neutrons and Solar Neutron Decay Protons
(2023) Y. Muraki; Tatsumi Koi; Y. Matsubara; S. Masuda; Pedro Miranda; Shoko Miyake; T. Naito; Ernesto Ortiz Fragoso; A. Oshima; T. Sako
Solar flares are broadly classified as impulsive or gradual. Ions accelerated in a gradual flare are thought to be accelerated through a shock acceleration mechanism, but the particle acceleration process in an impulsive flare is still largely unexplored. To understand the acceleration process, it is necessary to measure the high-energy gamma-rays and neutrons produced by the impulsive flare. Under such circumstances, on November 7, 2004, a huge X2.0 flare occurred on the solar surface, where ions were accelerated to energies greater than 10 GeV. The accelerated primary protons collided with the solar atmosphere and produced line gamma-rays and neutrons. These particles were received as neutrons and line gamma-rays, respectively. Neutrons of a few GeV, on the other hand, decay to produce secondary protons while traveling 0.06 au in the solar-terrestrial space. These secondary protons arrived at the magnetopause. Although the flux of secondary protons is very low, the effect of collecting secondary protons arriving in a wide region of the magnetosphere (the Funnel or Horn effect) has resulted in significant signals being received by the solar neutron telescope at Mt. Sierra Negra (4,600 m). This information suggests that ions on the solar surface are accelerated to over 10 GeV with an impulsive flare.
Detection of Solar Neutrons and Solar Neutron Decay Protons
(Multidisciplinary Digital Publishing Institute, 2023) Y. Muraki; Tatsumi Koi; S. Masuda; Y. Matsubara; Pedro Miranda; Shoko Miyake; T. Naito; E. Ortiz; A. Oshima; T. Sako
Solar flares are broadly classified as impulsive or gradual. Ions accelerated in a gradual flare are thought to be accelerated through a shock acceleration mechanism, but the particle acceleration process in an impulsive flare is still largely unexplored. To understand the acceleration process, it is necessary to measure the high-energy gamma rays and neutrons produced by the impulsive flare. Under such circumstances, on 7 November 2004, a huge X2.0 flare occurred on the solar surface, where ions were accelerated to energies greater than 10 GeV. The accelerated primary protons collided with the solar atmosphere and produced line gamma rays and neutrons. These particles were received as neutrons and line gamma rays, respectively. Neutrons of a few GeV, on the other hand, decay to produce secondary protons while traveling 0.06 au in the solar–terrestrial space. These secondary protons arrive at the magnetopause. Although the flux of secondary protons is very low, the effect of collecting secondary protons arriving in a wide region of the magnetosphere (the Funnel or Horn effect) has resulted in significant signals being received by the solar neutron telescope at Mt. Sierra Negra (4600 m). This information suggests that ions on the solar surface are accelerated to over 10 GeV with an impulsive flare.
Highly significant detection of solar neutrons on 2005 September 7
(Elsevier BV, 2007) K. Watanabe; T. Sako; Y. Muraki; Y. Matsubara; T. Sakai; S. Shibata; Jose F. Valdés Galicia; L. X. González; A. Hurtado; O. Musalém
Long-lived Solar Neutron Emission in Comparison with Electron-produced Radiation in the 2005 September 7 Solar Flare
(IOP Publishing, 2006) T. Sako; K. Watanabe; Y. Muraki; Y. Matsubara; H. Tsujihara; M. T. Yamashita; T. Sakai; S. Shibata; Jose F. Valdés Galicia; L. X. González
Strong signals of neutral emissions were detected in association with a solar flare that occurred on 2005 September 7. They were produced by both relativistic ions and electrons. In particular, relativistic neutrons were observed with the solar neutron telescopes (SNTs) located at Mount Chacaltaya in Bolivia and Mount Sierra Negra in Mexico and with neutron monitors (NMs) at Chacaltaya and Mexico City with high statistical significances. At the same time, hard X-rays and γ-rays, which were predominantly emitted by high-energy electrons, were detected by the Geotail and the INTEGRAL satellites. We found that a model of the impulsive neutron emission at the time of the X-ray/γ-ray peak can explain the main peaks of all the detected neutron signals, but failed to explain the long tailed decaying phase. An alternative model, in which the neutron emission follows the X-ray/γ-ray profile, also failed to explain the long tail. These results indicate that the acceleration of ions began at the same time as the electrons but that ions were continuously accelerated or trapped longer than the electrons in the emission site. We also demonstrate that the neutron data observed by multienergy channels of SNTs put constraints on the neutron spectrum.
Physics of ion acceleration in the solar flare on 2005 September 7 determines γ-ray and neutron production
(Elsevier BV, 2009) K. Watanabe; R. P. Lin; Säm Krucker; R. J. Murphy; G. H. Share; Mark Harris; M. Gros; Y. Muraki; T. Sako; Y. Matsubara
Proton Penetration Efficiency over Sierra Negra (Mexico) and Oulu (Finland)
(2023) Y. Muraki; Shoko Miyake; T. Koi; Y. Matsubara; S. Masuda; P. Miranda; T. Naito; E. Ortiz; A. Oshima; T. Sako
On November 7, 2004, a large solar flare was observed, which had a notable impact on the solar neutron detectors located at Mt. Chacaltaya (5,250 m) in Bolivia and Mt. Sierra Negra (4,600 m) in Mexico. In addition, the neutron monitor at Oulu, Finland, recorded a 5-sigma enhancement. In order to determine the causes of these enhancements, we performed trajectory simulations ejecting anti-protons from 20 km above each location, and checked whether or not these anti-protons could reach the magnetopause (∼8𝑅E). Then, we understand that the Chacaltaya enhancement was caused by solar neutrons themselves, while the Mt. Sierra Negra event may have been produced by high-energy solar neutron decay protons (SNDPs) with energies ≥ 6 GeV. Based on our anti- proton trajectory analysis, we suggest that the enhancement at Oulu may also have been produced by solar neutron decay protons with energies around ≥ 200 MeV. During this flare, protons were accelerated up to 10 GeV within one minute, leading to the production of SNDPs.
Solar Neutron Decay Protons Observed in November 7, 2004
(2021) Y. Muraki; Jose F. Valdés Galicia; E. Ortiz; Y. Matsubara; S. Shibata; T. Sako; S. Masuda; Shoko Miyake; M. Tokumaru; Tatsumi Koi
We have found an interesting event registered by the solar neutron telescopes installed at high mountains in Bolivia (5250 m a.s.l.) and Mexico (4600 m a.s.l.). The event was observed on November 7th of 2004 in association with a large solar flare of magnitude X2.0. Some features in the registers reveal the presence of solar neutrons, but also possible solar neutron decay protons (SNDP). SNDPs were recorded on board ISEE3 satellite in June 3rd, 1982 . On October 19th, 1989, the ground level detectors installed in Goose Bay and Deep River revealed the registration of SNDPs. Therefore this is the second example that such an evidence is registered on the Earth’s surface.
Solar Neutron Event in Association with a Large Solar Flare on 2000 November 24
(IOP Publishing, 2003) K. Watanabe; Y. Muraki; Y. Matsubara; Kazuaki Murakami; T. Sako; H. Tsuchiya; S. Masuda; M. Yoshimori; N. Ohmori; P. Miranda
Solar neutrons have been detected using the neutron monitor located at Mt. Chacaltaya, Bolivia, in association with a large solar flare on November 24, 2000. This is the first detection of solar neutrons by the neutron monitor that have been reported so far in solar cycle 23. The statistical significance of the detection is 5.5 sigma. In this flare, the intense emission of hard X-rays and gamma-rays has been observed by the Yohkoh Hard X-ray Telescope (HXT) and Gamma Ray Spectrometer (GRS), respectively. The production time of solar neutrons is better correlated with those of hard X-rays and gamma-rays than with the production time of soft X-rays. The observations of the solar neutrons on the ground have been limited to solar flares with soft X-ray class greater than X8 in former solar cycles. In this cycle, however, neutrons were detected associated with an X2.3 solar flare on November 24, 2000. This is the first report of the detection of solar neutrons on the ground associated with a solar flare with its X-ray class smaller than X8.
Solar neutron events in association with large solar flares in November 2003
(Elsevier BV, 2005) K. Watanabe; Y. Muraki; Y. Matsubara; Kazuaki Murakami; T. Sako; P. Miranda; R. Ticona; A. Velarde; F. Kakimoto; S. Ogio
Status of the world-wide network of solar neutron telescopes in solar cycle 24
(2009) Y. Matsubara; Y. Muraki; T. Sako; Y. Itow; T. Sakai; S. Shibata; T. Yuda; M. Ohnishi; H. Tsuchiya; Y. Katayose
A network of solar neutron telescopes has been developed since the middle of solar cycle 22. We have detected several important solar neutron events until the end of solar cycle 23 using solar neutron telescopes, but the accumulation of more solar neutron events is indispensable to eclucidate the acceleration mechanism of high energy particles. The data of the solar magnetic field with a space resolution of 0.3 arcsec obtained by Hinode satellite will be useful to understand solar neutron events more efficiently than during the previous solar cycles. In this paper we discuss the expected scientific results obtained by the world-wide network of solar neutron telescopes during solar cycle 24.