Systematic study of high energy cosmic-ray sources

获得国家重点科研资助项目（712）的支持，与中国科学家合作，在西藏羊八井（海拔4300米）建设了高灵敏度空气淋浴阵列和太阳中子望远镜。该研究项目的主要目的是寻找来自活动天体的高能伽马射线，研究高能银河系宇宙射线，并观察与太阳耀斑有关的高能中子。这些观测对于澄清宇宙射线的起源及其在源头的加速机制具有重要的意义，这两个问题目前仍未得到解决。1998年以前建造的“西藏- 0”风淋阵从1999年开始逐步升级和改进，增加了新的探测器，并于2003年完工。目前的阵列（Tibet-III）由大约800个闪烁探测器组成，部署在间距为7.5米的网格上，覆盖面积为37000平方米。风淋事件的触发率设定为约1.7kHz…More，在3 TeV以上的能量区域，每个事件的到达方向可以以小于0.9度的误差估计。太阳中子望远镜于1999年建成，并连续运行至今。在这个太阳活动周期中观测到一些耀斑中子事件。到目前为止取得的重要成果如下：1)从蟹状星云和活动星系核imrk421和Mrk501中先后观测到约3tev以上的高能伽马射线。这是世界上首次用空气淋室阵列观测伽玛射线源。2)首次观测到银河系宇宙射线的大尺度各向异性的能量依赖性，并在天鹅座区方向观测到明显的多tev宇宙射线各向异性。3)观测了全粒子和质子在膝盖周围的能谱。这些结果强烈表明，随着膝盖区域初级能量的增加，初级成分变得更加重要。4)利用风淋阵连续监测了第23个太阳活动周期内太阳阴影的变化，清楚地观测到在太阳活动极大期出现了一种特殊的变化，称为格涅维雪夫间隙。5)利用太阳中子望远镜探测到与太阳耀斑相关的中子。与GOES卫星x射线观测结果的比较表明，在某种太阳耀斑中可能产生能量超过10 GeV的高能中子。这是世界上第一次观测，与宇宙射线的起源和加速，宇宙射线在太阳和行星际磁场以及银河系中的传播有关，并发表在国际期刊上。我们在国际会议和/或研讨会以及日本物理学会I的会议上报告了这些结果。我们对1999年至2005年的科研成果作了总结报告。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