The Sun was intensely active from late October to the beginning of November 2003. A series of 11 X class solar flares occurred in NOAA regions 484, 486 and 488. Unique among this series of flares were those occurring on November 2 and 4 in which solar neutrons were observed by the ground based neutron monitors located at Mt. Chacaltaya, Bolivia and Haleakala, Hawaii, respectively. In these flares, intense emission of hard X-rays and γ-rays have been observed by the satellites. It seems that production of solar neutrons coincided with the production of the hard electromagnetic radiations of these two flares.
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The authors thank the RHESSI team for their support of the mission and their guidance in the analysis of the RHESSI satellite data. We appreciate the Geotail group and Prof. Terasawa for providing us with the data of the Geotail/LEP. K. Watanabe’s work is supported by the Grant-in-Aid program of the Japan Society for the Promotion of Science Fellows. This work is partially supported by a grant from the Ministry of Education, Culture, Sports, Science and Technology, Japan (Dynamics of the Sun–Earth–Life Interactive System, No. G-4, the 21st Century COE Program).