arXiv 1302.12842013-02astro-ph.SR

在2006 - 2009年不寻常的太阳极小期期间日光层银河质子的调制

Modulation of galactic protons in the heliosphere during the unusual solar minimum of 2006 to 2009

M. S. Potgieter, E. E. Vos, M. Boezio, N. De Simone, V. Di Felice, V. Formato

DOI：: 10.1007/s11207-013-0324-6

摘要：

最近一次太阳活动极小期以及随之而来的宇宙射线最小调制条件是不寻常的。2009年底在地球上记录到了银河系质子的最高水平，这与预期相反。介绍了2006年至2009年从Resurs-DK 1号卫星上搭载的PAMELA宇宙射线探测器观测到的质子谱，以及太阳调制宇宙射线综合数值模型的解。该模型用于确定在此期间质子调制的主要机制，以及为什么2009年观测到的光谱是有史以来最高的。从2006年中期到2009年12月，我们发现光谱变得明显变软，因为越来越多的低能质子到达了地球。为了模拟这种效应，扩散系数的刚性依赖性必须显著降低到~3 GeV以下。因此，2009年的调制最小期可以被描述为比以前的太阳极小期相对更多的“扩散主导”。然而，我们说明，漂移仍然发挥了重要作用，但可观察到的调制效应并不像以前那样与日光层电流片的波度相关。质子仍然经历着全球梯度和曲率漂移，因为直到2009年底，日光层磁场已经显著下降，而在以前的最低时期观察到的是适度下降。我们的结论是，所有调制过程都有助于在此期间观察到的质子光谱的增加，表现出这些主要机制的有趣的相互作用。

英文摘要：

The last solar minimum activity period, and the consequent minimum modulation conditions for cosmic rays, was unusual. The highest levels of galactic protons were recorded at Earth in late 2009 in contrast to expectations. Proton spectra observed for 2006 to 2009 from the PAMELA cosmic ray detector on-board the Resurs-DK1 satellite are presented together with the solutions of a comprehensive numerical model for the solar modulation of cosmic rays. The model is used to determine what mechanisms were mainly responsible for the modulation of protons during this period, and why the observed spectrum for 2009 was the highest ever recorded. From mid-2006 until December 2009 we find that the spectra became significantly softer because increasingly more low energy protons had reached Earth. To simulate this effect, the rigidity dependence of the diffusion coefficients had to decrease significantly below ~3 GeV. The modulation minimum period of 2009 can thus be described as relatively more "diffusion dominated" than previous solar minima. However, we illustrate that drifts still had played a significant role but that the observable modulation effects were not as well correlated with the waviness of the heliospheric current sheet as before. Protons still experienced global gradient and curvature drifts as the heliospheric magnetic field had decreased significantly until the end of 2009, in contrast to the moderate decreases observed during previous minimum periods. We conclude that all modulation processes contributed to the observed increases in the proton spectra for this period, exhibiting an intriguing interplay of these major mechanisms.

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