Observation of solar neutrons at high altitudes near the equator

本研究旨在通过在地面观测加速质子与太阳大气相互作用产生的高能太阳中子（>100MeV），阐明太阳表面高能粒子的加速机制。用中子而不是质子来研究太阳加速度更可取，因为中子不被行星际磁场反射。为了有效地探测太阳中子，以名古屋大学日地环境实验室为主体的研究小组，在世界范围内完成了对太阳进行全天观测的太阳中子探测器网络。这些探测器位于赤道附近的高山上，因为太阳中子在空气中传播时会衰减。根据科学研究补助金，玻利维亚Chacaltaya的太阳中子探测器的数据采集系统，设计于15年前，已被一个相当新的系统所取代，其中更丰富的是，数据采集在停电后自动启动。Chacaltaya（海拔5250米，南纬16度）是我们观测太阳中子的最佳地点。这一经验有助于在墨西哥塞拉内格拉的探测器上采用相同的系统，那里没有人永久居住。内格拉山脉（海拔4600米，北纬19度）是观测太阳中子的第二佳地点。这些新系统被认为能在2007年开始的下一个太阳活动周期中正常工作，我们将比以前更有效地探测太阳中子。当我们正在改进这两个系统时，2005年9月7日发生了一次大的太阳耀斑。Chacaltaya和Sierra Negra的太阳中子探测器都成功地探测到了太阳中子信号，这是迄今为止我国探测器获得的最重要的太阳中子信号。此外，查卡尔塔亚和墨西哥城的中子监测器也探测到明确的信号。对这类事件的分析目前还在进行中，但获得这类事件正是我们这项科研资助的目标。少

This research aims to clarify the acceleration mechanism of high energy particles at the solar surface, by observing on the ground high energy solar neutrons (>100MeV) produced by the interaction between accelerated protons and the solar atmosphere. It is more preferable to use neutrons than protons to study solar acceleration, because neutrons are not reflected by the interplanetary magnetic field. In order to detect solar neutrons effectively, the group which mainly includes Solar-Terrestrial Environment Laboratory, Nagoya University, has completed a network of solar neutron detectors in the world to observe the Sun for a whole day. These detectors are located at high mountains near the equator, because solar neutrons are attenuated while propagating in the air. According to the Grant-in-Aid for Scientific Research, the data taking system of the solar neutron detector at Chacaltaya in Bolivia, which was designed more than 15 years ago, has been replaced by a quite a new system, by wh … More ich a data taking starts automatically after a power cut of the electricity. Chacaltaya (altitude : 5250m, latitude : 16 degrees S) is the best place to observe solar neutrons in our network. This experience was useful to adopt the same system to the detector at Sierra Negra in Mexico, where nobody stays permanently. Sierra Negra (altitude : 4600m, latitude : 19 degrees N) the second best place to observe solar neutrons. These new systems are believed to work properly during the next solar cycle, which will start in 2007, and, we bacame to detect solar neutrons much more efficiently than before. While we were improving both systems, a large solar flare occurred on September 7, 2005. The solar neutron detectors both at Chacaltaya and Sierra Negra have succeeded in detecting solar neutron signals, which are the most significant ones so far obtained by our detectors. Moreover, neutron monitors at Chacaltaya and Mexico City also detected clear signals. The analysis on this events is now in progress, but obtaing this kind of event is what we have aimed by this Grant-in-Aid for Scientific Research. Less