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.
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The authors appreciate the work of our colleagues who manage and maintain the solar neutron telescopes. We also thank the INTEGRAL team for their support of the mission and for their guidance in the analysis of the INTEGRAL satellite data. K. Watanabe’s work is supported by the Grant-in-Aid program of the Japan Society for the Promotion of Science Fellows. This work was supported by a Grant-in-Aid for Scientific Research on Priority Area (11203204) by the Ministry of Education, Culture, Sports, Science, and Technology of Japan and by a Grant-in-Aid for Scientific Research (16540242) by the Japan Society for the Promotion of Science. This research was partly supported by a Nihon University Multidisciplinary Global Research Grant for 2001 and 2002, and by DGAPA UNAM grant 115303. Finally, the authors thank to the anonymous referee for his/her useful comments that improved our manuscript.