A phenomenological study of the long-term cosmic ray modulation, 850-1958 AD
A phenomenological study of the long-term cosmic ray modulation, 850-1958 AD
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DOI：
10.1029/2004ja010685
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发表时间：
2004-12
影响因子：
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通讯作者：
K. Mccracken;F. Mcdonald;J. Beer;G. Raisbeck;F. Yiou
中科院分区：
文献类型：
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作者：
K. Mccracken;F. Mcdonald;J. Beer;G. Raisbeck;F. Yiou
[1] 使用来自格陵兰岛和南极的 10Be 数据研究了过去 1150 年银河宇宙辐射的调制。为此，我们引入使用22年平均值来研究长期调制。考虑到地磁偶极子的长期变化后，结果表明，在奥尔特（公元1050年）、斯波尔（1420-1540）和蒙德（1645-1715）低太阳周期的后半段相距很远的时期，1-2 GeV/核子附近的银河宇宙辐射（GCR）的22年平均强度恢复到大致相同的高水平。活动。就调制势 ψ 而言，该渐近强度对应于~84 MV 的平均残余调制。 GCR 强度在 Wolf (∼1320) 和 Dalton (1810) 极小值以及 ψ∼200 MV 期间显着降低。来自格陵兰岛的较高时间分辨率数据显示，在斯波勒和蒙德极小期（Δψ ≈ 200-300 MV）期间，这些高强度叠加了 11 年的大波动和其他波动，表明持续存在大量且与时间相关的日磁场。在整个斯波勒极小期间，GCR强度反复回到非常低的调制状态，表明入射到地球的宇宙线光谱接近当地星际光谱的水平。这些结果意味着在整个低太阳活动期间，（1）日光层电流片的正常循环变化和/或（2）扩散系数的循环变化持续存在（或两者）。数据表明，仪器时代（1933 年至今）宇宙射线强度的调制（即减弱）是过去 1150 年中最大的之一。此外，自公元 850 年以来，在之前的五次相距甚远的情况下，已经达到了大致相同的低值，我们推测日光层磁场在那些时间已经达到了渐近极限。 10Be 数据表现出一个以前未被认识到的特征，我们将其命名为“急剧下降”，其中 1-2 GeV/核子强度在 1700 年至 1739 年间下降了约 40-45%，对应于 Δψ > 500 MV，此时太阳活动较低但不断增加。直到 1950 年太阳活动高峰期之后，才再次观测到比 1739 年低的宇宙射线强度。这些特征以及斯波勒和蒙德极小期期间的大型 11 年调制事件表明，GCR 强度的长期变化与太阳活动低时期的黑子数量关系不大。结果表明，10Be数据的变化与Schrijver等人预测的开放太阳磁通量的变化之间有更好的一致性。 [2002] 和 Solanki 等人。 [2002] 基于历史太阳黑子数量的模型。特别是，它们都表现出与 10Be 数据的急剧下降一致的特征，尽管幅度小于 10Be 数据所暗示的。
[1] The modulation of the galactic cosmic radiation over the past 1150 years is investigated using 10Be data from Greenland and the South Pole. For this purpose, we introduce the use of 22-year averages to study the long-term modulation. After allowance for secular changes in the geomagnetic dipole, it is shown that the 22-year mean intensity of the galactic cosmic radiation (GCR) in the vicinity of 1–2 GeV/nucleon returned to approximately the same high level at the widely separated times of the Oort (1050 AD), Spoerer (1420–1540), and the latter portion of the Maunder (1645–1715) periods of low solar activity. In terms of the modulation potential, ϕ, this asymptotic intensity corresponds to a mean residual modulation of ∼84 MV. The GCR intensity was significantly less during the Wolf (∼1320) and Dalton (1810) minima, and ϕ ∼ 200 MV. The higher temporal resolution data from Greenland shows that there were large 11-year and other fluctuations superimposed upon these high intensities during the Spoerer and Maunder minima (Δϕ ≈ 200–300 MV), indicating the continued presence of a substantial and time-dependent heliomagnetic field. Throughout the Spoerer minimum, the GCR intensity repeatedly returned to a condition of very low modulation, indicating that the cosmic ray spectrum incident on the Earth approached the level of the local interstellar spectrum. These results imply the continued presence of either (or both) (1) the normal cyclic variation of the heliospheric current sheet and/or (2) a cyclic variation of the diffusion coefficients throughout these periods of low solar activity. The data indicate that the modulation (i.e., depression) of the cosmic ray intensity during the instrumental era (1933–present) has been one of the greatest in the past 1150 years. Further, approximately the same low value has been attained on five previous widely separated occasions since 850 AD, and we speculate that the heliospheric magnetic field has reached an asymptotic limit at those times. The 10Be data exhibit a previously unrecognized feature, which we have named “the precipitous decrease,” in which the 1–2 GeV/nucleon intensity decreased by ∼40–45% between 1700 and 1739 corresponding to Δϕ > 500 MV, at a time of low but increasing solar activity. A lower cosmic ray intensity than that attained in 1739 was not observed again until after 1950, at a time of high solar activity. These features and the large 11-year modulation events during the Spoerer and Maunder minima indicate that the long-term variations in the GCR intensity are poorly related to sunspot number during epochs of low solar activity. It is shown that there is better agreement between the variations in the 10Be data, and the changes in the open solar magnetic flux predicted by the Schrijver et al. [2002] and Solanki et al. [2002] models based on historic sunspot numbers. In particular, they both exhibit characteristics consistent with the precipitous decrease in the 10Be data, although the amplitudes are smaller than implied by the 10Be data.