SOLAR CYCLE DEPENDENCE OF THE DIURNAL ANISOTROPY OF 0.6 TeV COSMIC-RAY INTENSITY OBSERVED WITH THE MATSUSHIRO UNDERGROUND MUON DETECTOR
SOLAR CYCLE DEPENDENCE OF THE DIURNAL ANISOTROPY OF 0.6 TeV COSMIC-RAY INTENSITY OBSERVED WITH THE MATSUSHIRO UNDERGROUND MUON DETECTOR
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DOI：
10.1088/0004-637x/712/2/1100
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发表时间：
2009-11
期刊：
影响因子：
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通讯作者：
K. Munakata;Y. Mizoguchi;C. Kato;S. Yasue;S. Mori;M. Takita;J. Kota
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文献类型：
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作者：
K. Munakata;Y. Mizoguchi;C. Kato;S. Yasue;S. Mori;M. Takita;J. Kota
我们分析了在1985-2008年两个完整的太阳活动周期中，使用Matsushiro（日本）地下μ子探测器观测到的亚TeV宇宙线强度的日各向异性的时间变化。我们发现一个各向异性分量叠加在康普顿各向异性由于地球绕太阳的轨道运动的太阳日各向异性。这种额外的各向异性的相位在当地太阳时0.15：00几乎是恒定的，对应于垂直于地球轨道平均行星际磁场的方向，而振幅在最大值（0.043% ± 0.002%）和最小值（0.008% ± 0.002%）之间变化，与太阳活动有明显的相关性。我们发现振幅的时间变化和太阳黑子数（SSN）之间有一个显着的时间滞后，并获得最佳的相关系数为+0.74与SSN延迟26个月。我们认为，这种各向异性可能被解释的能量变化，由于太阳风引起的电场预期银河宇宙射线（GCR）穿越波浪中性片。整个周期的恒星日变化的平均振幅为0.034% ± 0.003%，这大约是从监测多TeV GCR强度的空气簇射和深地下μ子实验报告的振幅的三分之一，这表明由于太阳调制的各向异性的显着衰减。我们发现，另一方面，只有一个弱的正相关关系的恒星日各向异性和太阳活动周期中的振幅在“活跃”的太阳活动时期的两倍左右的振幅在“安静”的太阳活动时期。这意味着，只有四分之一的总衰减变化与太阳活动周期和/或太阳磁周期。最后，我们检查的时间变化的“单波段谷深”（SBVD）引用的米拉格罗实验，并在最近的米拉格罗的报告相比，我们发现在2000年和2007年之间的七年期间，在松代观测没有稳定的增长。因此，我们认为，稳定增加的SBVD报告的米拉格罗实验是不是由减少太阳调制在第23太阳活动周期的下降阶段。
We analyze the temporal variation of the diurnal anisotropy of sub-TeV cosmic-ray intensity observed with the Matsushiro (Japan) underground muon detector over two full solar activity cycles in 1985–2008. We find an anisotropy component in the solar diurnal anisotropy superimposed on the Compton–Getting anisotropy due to Earth's orbital motion around the Sun. The phase of this additional anisotropy is almost constant at ∼15:00 local solar time corresponding to the direction perpendicular to the average interplanetary magnetic field at Earth's orbit, while the amplitude varies between a maximum (0.043% ± 0.002%) and minimum (∼0.008% ± 0.002%) in a clear correlation with the solar activity. We find a significant time lag between the temporal variations of the amplitude and the sunspot number (SSN) and obtain the best correlation coefficient of +0.74 with the SSN delayed for 26 months. We suggest that this anisotropy might be interpreted in terms of the energy change due to the solar-wind-induced electric field expected for galactic cosmic rays (GCRs) crossing the wavy neutral sheet. The average amplitude of the sidereal diurnal variation over the entire period is 0.034% ± 0.003%, which is roughly one-third of the amplitude reported from air shower and deep-underground muon experiments monitoring multi-TeV GCR intensity suggesting a significant attenuation of the anisotropy due to the solar modulation. We find, on the other hand, only a weak positive correlation between the sidereal diurnal anisotropy and the solar activity cycle in which the amplitude in the “active” solar activity epoch is about twice the amplitude in the “quiet” solar activity epoch. This implies that only one-fourth of the total attenuation varies in correlation with the solar activity cycle and/or the solar magnetic cycle. We finally examine the temporal variation of the “single-band valley depth” (SBVD) quoted by the Milagro experiment and, in contrast with recent Milagro's report, we find no steady increase in the Matsushiro observations in a seven-year period between 2000 and 2007. We suggest, therefore, that the steady increase of the SBVD reported by the Milagro experiment is not caused by the decreasing solar modulation in the declining phase of the 23rd solar activity cycle.