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Solar flares are broadly classified into the impulsive flares and the gradual flares. Of these, the process by which ions are accelerated to high energies in the impulsive flares are not well understood. To elucidate this process, it is important to detect solar neutrons produced by solar flares. For this reason, we have installed instruments in high mountains all over the world to continue the observation.
The solar activity in the 25th solar cycle is now approaching at the peak, and X-class flares are frequently observed on the solar surface. As a result, high-energy ions are arriving on the Earth stations many times. In this paper, we report the neutron associated events at Mt. Norikura Observatory (2,700m) during 2004. These events were recorded on May 8 (X1)(twice), May 11 (X5.8), Oct 24 (X3.1) of 2024 and solar neutron decay proton event(SNDP) were recorded also in the neutron monitor at Calgary(SNDP) on May 11 of 2024.
Note that 1m^2 area 50cm thick scintillator and 12NM64 neutron monitor are currently used. They are automatically operated by the solar power generator in the winter season. We believe that our experience will be useful for other observing projects without electricity. Therefore, we also describe the details of this observation system in the paper.