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Advances in Astronomy
Volume 2012 (2012), Article ID 379304, 14 pages
http://dx.doi.org/10.1155/2012/379304
Research Article

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

1Solar-Terrestrial Environment Laboratory, Nagoya University, Nagoya 464-8601, Japan
2Tsukuba Space Center, JAXA, Tsukuba 305-8505, Japan
3Department of Physics, Tokyo Metropolitan University, Tokyo 192-0397, Japan
4Planetary Plasma and Atmospheric Research Center, Tohoku University, Sendai 980-8578, Japan
5Department of Information Science, Chubu University, Kasugai 487-8501, Japan
6Department of Physics, Konan University, Kobe 658-8501, Japan

Received 15 August 2012; Revised 14 October 2012; Accepted 29 November 2012

Academic Editor: Karel Kudela

Copyright © 2012 Y. Muraki et al. This is an open access article distributed under the Creative Commons Attribution License, which permits unrestricted use, distribution, and reproduction in any medium, provided the original work is properly cited.

Abstract

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.