Systematic study of high energy cosmic-ray sources

在优先领域科学研究补助金（712）的支持下，我们与中国科学家合作，在西藏羊八井（海拔4300米）建造了一个高灵敏度空气簇射阵列和一个太阳中子望远镜。该研究项目的主要目的是寻找来自活跃天体的高能伽马射线，研究甚高能银河宇宙射线，并观察与太阳耀斑有关的高能中子。这些观测对于弄清宇宙线的起源及其在源处的加速机制是非常重要的，这两个问题都是尚未解决的。1998年以前建造的空气簇射阵列（Tibet-10）从1999年开始逐步升级和改进，增加了新的探测器，并于2003年完成。目前的阵列（西藏-III）包括约800闪烁探测器，部署在一个网格的7.5米的间距，覆盖面积37000平方米。空气簇射事件的触发率被设置为约1.7kHz ...更多信息 并且在超过3 TeV的能量区域中，每个事件的到达方向可以以小于0.9度的不准确度被估计。太阳中子望远镜于1999年建成并已连续运行至今，在第23太阳活动周期间观测到了几次耀斑中子事件。迄今取得的重要成果如下：1）从蟹状星云和活动星系核Mrk 421和Mrk 501中连续观测到了3 TeV以上的高能γ射线。这是世界上首次用空气簇射阵观测γ射线源。2)首次观测到银河系宇宙线的大尺度各向异性与能量的关系，并在天鹅座方向观测到多TeV宇宙线的显著各向异性。3）观测到膝附近的所有粒子和质子的能谱。4）利用空气簇射阵连续观测到太阳活动23周期间日影的变化，并在太阳活动峰期观测到一个特殊的变化，称为格涅维舍夫间隙（Gnevyshev gap）。5）利用太阳中子望远镜观测到与耀斑有关的中子。与GOES卫星的X射线观测比较表明，在某种太阳耀斑中可能产生能量在10 GeV以上的极高能中子，这是世界上首次观测到的与宇宙线的起源和加速、宇宙线在太阳和行星际磁场中的传播以及宇宙线在银河系中的传播有关的现象，并发表在国际期刊上。我们在国际会议和/或讲习班上以及在日本物理学会I的会议上报告了这些情况。我们对1999年至2005年期间取得的科学成果作了总结报告。少

Gaining support of a Grant-in-Aid for Scientific Research on Priority Area (712), we constructed a high sensitivity airshower array and a solar neutron telescope at Yangbajing (4300 m a.s.1) in Tibet in collaboration with Chinese scientists. The main purposes of this research project is to search for high-energy gamma rays from active celestial objects, to study very high energy Galactic cosmic rays and to observe high energy neutrons in association with solar flares. These observations are very important to clarify the origin of cosmic rays and its acceleration mechanism at the sources, both of which remain unsolved yet The airshower array (Tibet-I0 constructed before 1998 was gradually upgraded and improved from 1999 by adding new detectors and completed in 2003. The present array (Tibet-III) consists of about 800 scintillation detectors which are deployed at a grid of 7.5 m spacing covering the area of 37000 square meters. The trigger rate of airshower events is set to about 1.7kHz … More and the arrival direction of each event can be estimated with an inaccuracy of less than 0.9 degrees in the energy region over 3 TeV. The solar neutron telescope was completed in 1999 and it has been successively operated until now A few flare neutron events were observed during this solar cycle 23.The important results obtained until now are as follows.1) High energy gamma rays above about 3 TeV have been successively observed from the Crab Nebula and active galactic nudeiMrk421 and Mrk501. This is the first observation of the gamma-ray sources with air shower array in the world..2) An energy dependence of the large-scale anisotropy of the Galactic cosmic rays has been for the first time observed and also significant anisotropy of multi-TeV cosmic rays is observed in the direction of Cygnus region.3) Energy spectra of all-particles and protons around the knee have been observed. These results strongly suggest that the primary composition becomes heavy dominant with increasing primary energy at the knee region.4) A variation of the sun shadow during the solar activity cycle 23 was successively monitored with the air shower array, and a peculiar change appeared at the solar maximum, called Gnevyshev gap, was clearly observed.5) Neutrons associated with solar flares were detected with the solar neutron telescope. A comparison with the x-ray observation with GOES satellite shows that very high energy neutrons with its energy above 10 GeV may be created at some kind of solar flares.These are the first observations in the world and are related with the origin and acceleration of cosmic rays, the propagation of cosmic rays in the solar and interplanetary magnetic fields as well as in the Galaxy, and were published in the international journals. We reported these at the international conferences and/or workshops and also at the meetings of the Physical Society I of Japan. We made a summary report on the scientific results obtained during the period from 1999 through 2005. Less