S. Shibata

Measurement by FIB on the ISS: Two Emissions of Solar Neutrons Detected?

A new type of solar neutron detector (FIB) was launched on board the Space Shuttle Endeavour on July 16, 2009, and began collecting data at the International Space Station (ISS) on August 25, 2009. This paper summarizes the three years of observations obtained by the solar neutron detector FIB until the end of July 2012. The solar neutron detector FIB can determine both the energy and arrival direction of neutrons. We measured the energy spectra of background neutrons over the South Atlantic Anomaly (SAA) region and elsewhere and found the typical trigger rates to be 20 and 0.22 counts/sec, respectively. It is possible to identify solar neutrons to within a level of 0.028 counts/sec, provided that directional information is applied. Solar neutrons were possibly observed in association with the M-class solar flares that occurred on March 7 (M3.7) and June 7 (M2.5) of 2011. This marked the first time that neutrons had been observed in M-class solar flares. A possible interpretation of the production process is provided.

Performance of the SciBar cosmic ray telescope (SciCRT) toward the detection of high-energy solar neutrons in solar cycle 24

We plan to observe solar neutrons at Mt. Sierra Negra (4,600 m above sea level) in Mexico using the SciBar detector. This project is named the SciBar Cosmic Ray Telescope (SciCRT). The main aims of the SciCRT project are to observe solar neutrons to study the mechanism of ion acceleration on the surface of the sun and to monitor the anisotropy of galactic cosmic-ray muons. The SciBar detector, a fully active tracker, is composed of 14,848 scintillator bars, whose dimension is 300 cm × 2.5 cm × 1.3 cm. The structure of the detector enables us to obtain the particle trajectory and its total deposited energy. This information is useful for the energy reconstruction of primary neutrons and particle identification. The total volume of the detector is 3.0 m × 3.0 m × 1.7 m. Since this volume is much larger than the solar neutron telescope (SNT) in Mexico, the detection efficiency of the SciCRT for neutrons is highly enhanced. We performed the calibration of the SciCRT at Instituto Nacional de Astrofisica, Optica y Electronica (INAOE) located at 2,150 m above sea level in Mexico in 2012. We installed the SciCRT at Mt. Sierra Negra in April 2013 and calibrated this detector in May and August 2013. We started continuous observation in March 2014. In this paper, we report the detector performance as a solar neutron telescope and the current status of the SciCRT.

Regional climate pattern during two millennia estimated from annual tree rings of Yaku cedar trees: a hint for solar variability?

We analyzed trees that have survived on Yaku island (Yakushima) for 2,000 years. Quite surprisingly, the Fourier and wavelet analyses of the annual growth rate identified 2 cycles of periodicities of 11 and (24 ± 4) years during the Oort, Wolf, Spörer, Maunder, and Dalton minima. The 11-year periodicity originated from solar activity, while the (24 ± 4)-year periodicity may be related to the Pacific Decadal Oscillation (PDO). In particular, we have discovered an 11-year periodicity in the meteorological daylight-hour data from Yakushima in the month of June during 1938 to 2013 and a 24-year periodicity in July. The growth rate of the tree rings may be affected by the variation of the daylight hour.Rings Y. Murakia∗, T. Mitsutani, S. Kuramata, K. Masuda, K. Nagaya, and S. Shibata a Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601, Japan Nara National Research Institute for Cultural Properties, Nara 630-8577, Japan Faculty of Science and Technology, Hirosaki University, Hirosaki 036-8561, Japan Engineering Science Laboratory, College of Engineering, Chubu University, Kasugai 487-0027, Japan

Analysis of solar gamma rays and solar neutrons detected on March 7th and September 25th of 2011 by ground level neutron telescopes, SEDA-FIB and FERMI-LAT

At the 33rd ICRC, we reported the possible detection of solar gamma rays by a ground level detector and later re-examined this event. On March 7, 2011, the solar neutron telescope (SNT) located at Mt. Sierra Negra, Mexico (4,600 m) observed enhancements of the counting rate from 19:49 to 20:02 UT and from 20:50 to 21:01 UT. The statistical significance was 9.7sigma and 8.5sigma, respectively. This paper discusses the possibility of using this mountain detector to detect solar gamma rays. In association with this event, the solar neutron detector SEDA-FIB onboard the International Space Station has also detected solar neutrons with a statistical significance of 7.5sigma. The FERMI-LAT detector also observed high-energy gamma rays from this flare with a statistical significance of 6.7sigma. We thus attempted to make a unified model to explain this data. In this paper, we report on another candidate for solar gamma rays detected on September 25th, 2011 by the SNT located in Tibet (4,300 m) from 04:37 to 04:47 UT with a statistical significance of 8.0sigma (by the Li-Ma method).

Angular Distribution of Solar Gamma Rays and Solar Neutrons Simulated by GEANT4 Program

When the accelerated protons hit the solar surface, high-energy gamma-rays and neutrons are produced. However observed intensity of gamma-rays and neutrons at the Earth depends on not only the position of the flare on the solar surface but also the direction of the accerelated protons and helium ions. Without precise knowledge of the angular distribution of secondary particles, we cannot estimate correct intensity of accelerated ions. Therefore we have made a Monte Carlo simulation based on the GEANT 4 program to understand the angular distribution induced by the proton-solar atmosphere and the helium-solar atomosphere collisions.

Transient weakening of geomagnetic shield probed by GRAPES-3 experiment

The large area (560 m

Diffusion of cosmic rays in heliosphere, observations from GRAPES-3

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Development of faster front end electronics for the SciCRT detector at Sierra Negra, Mexico

) GRAPES-3 tracking muon telescope in Ooty, India recorded a 2 hour (h) muon burst on 22 June 2015 starting at 19:00 UT in the midst of a continuing Forbush decrease. The burst occurred following the arrival of a coronal mass ejection containing a 40 nT south-ward interplanetary magnetic field (IMF) that had triggered a G4 class geomagnetic storm. During the 2 hour, the muon telescope recorded an excess of

Sensitivity of the SciBar Cosmic Ray Telescope (SciCRT) to solar neutrons

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Extending the range of particle densities observed by GRAPES-3

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