Solar semidiurnal anisotropy of galactic cosmic ray intensity observed by the two‐hemisphere network of surface‐level muon telescopes
Solar semidiurnal anisotropy of galactic cosmic ray intensity observed by the two‐hemisphere network of surface‐level muon telescopes
复制标题
地表μ介子望远镜双半球网络观测到的银河系宇宙线强度的太阳半日各向异性
DOI：
10.1029/98ja01926
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发表时间：
1998
期刊：
影响因子：
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通讯作者：
M. Duldig
中科院分区：
文献类型：
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作者：
K. Munakata;T. Kitawada;S. Yasue;S. Mori;C. Kato;M. Koyama;S. Akahane;D. Hall;Z. Fujii;K. Fujimoto;J. Humble;A. G. Fenton;K. Fenton;M. Duldig
利用霍巴特(澳大利亚塔斯马尼亚)和名古屋(日本爱知)表面水平多方向Muon望远镜的两个半球网络的观测结果，研究了宇宙线强度半日变化的来源。这个网络使我们能够精确地确定两个半球变化的不对称性。结果表明，这种变化与空间宇宙线强度的南北对称分布是一致的。引起变化的空间调和矢量的相位既与双向纬度密度梯度(类型I)预期的二阶各向异性一致，也与由俯仰角散射(类型II)引起的各向异性一致。该网络还观察到了一个纯粹的NS反对称的、反恒星的日变化，两个半球之间的最大相位相差12小时。这与由二阶各向异性产生的太阳日变化的年度调制所产生的反恒星日变化是一致的。负责反恒星日变化的空间调和矢量的相位与从I型和II型各向异性中预测的相位是一致的。结果表明，反恒星日变化的空间调和矢量的振幅与太阳半日变化的振幅之比符合II型各向异性，而不符合I型各向异性。这一结果表明，1992-1995年期间观测到的太阳半日变化和反恒星日变化主要是由II型各向异性引起的，不能仅仅解释为由I型各向异性引起。
Observations made by the two-hemisphere network of surface-level, multidirectional muon telescopes at Hobart (Tasmania, Australia) and Nagoya (Aichi, Japan) are used to examine the origin of the solar semidiurnal variation in cosmic ray intensity. The network allows us to precisely determine the asymmetry of the variation across both hemispheres. It is shown that the variation is consistent with the north–south (NS) symmetric distribution of cosmic ray intensity in space. The phase of the space harmonic vector responsible for the variation is consistent with both the second-order anisotropy expected from a bidirectional latitudinal density gradient (type I) and also one arising from pitch angle scattering (type II). The network also observed a purely NS antisymmetric, antisidereal diurnal variation with the maximum phases differing by 12 hours between the two hemispheres. This is consistent with an antisidereal diurnal variation arising from annual modulation of the solar diurnal variation produced by a second-order anisotropy. The phase of the space harmonic vector responsible for the antisidereal diurnal variation is consistent with the phases predicted from both type I and type II anisotropies. It is shown, however, that the ratio of the amplitude of the space harmonic vector of the antisidereal diurnal variation to that of the solar semidiurnal variations is consistent with the type II anisotropy but not with the type I anisotropy. This result implies that the solar semidiurnal variation and the antisidereal diurnal variation observed during the period 1992–1995 mainly arise from the type II anisotropy and cannot be explained solely as arising from the type I anisotropy.