We demonstrate that global observations of high‐energy cosmic rays contribute to understanding unique characteristics of a large‐scale magnetic flux rope causing a magnetic storm in August 2018. Following a weak interplanetary shock on August 25, 2018, a magnetic flux rope caused an unexpectedly large geomagnetic storm. It is likely that this event became geoeffective because the flux rope was accompanied by a corotating interaction region and compressed by high‐speed solar wind following the flux rope. In fact, a Forbush decrease was observed in cosmic‐ray data inside the flux rope as expected, and a significant cosmic‐ray density increase exceeding the unmodulated level before the shock was also observed near the trailing edge of the flux rope. The cosmic‐ray density increase can be interpreted in terms of the adiabatic heating of cosmic rays near the trailing edge of the flux rope, as the corotating interaction region prevents free expansion of the flux rope and results in the compression near the trailing edge. A northeast‐directed spatial gradient in the cosmic‐ray density was also derived during the cosmic‐ray density increase, suggesting that the center of the heating near the trailing edge is located northeast of Earth. This is one of the best examples demonstrating that the observation of high‐energy cosmic rays provides us with information that can only be derived from the cosmic ray measurements to observationally constrain the three‐dimensional macroscopic picture of the interaction between coronal mass ejections and the ambient solar wind, which is essential for prediction of large magnetic storms.

中文翻译：

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全球Muon探测器网络观察到了2018年8月的一次奇特的ICME活动

我们证明，对高能宇宙射线的全球观测有助于理解2018年8月引起磁暴的大型磁通量绳索的独特特征。在2018年8月25日的弱行星际震荡之后，磁通量绳索意外地引起了大型地磁风暴。该事件可能具有地质效应，因为磁通量绳伴随着一个共同旋转的相互作用区域，并被磁通量绳后面的高速太阳风压缩。实际上，正如预期的那样，在通量绳内部的宇宙射线数据中观察到了Forbush下降，并且在通量绳后缘附近还观察到冲击之前，宇宙射线密度显着增加，超过了未调制的水平。宇宙射线密度的增加可以用通量绳尾缘附近的宇宙射线的绝热加热来解释，因为同向相互作用区域阻止通量绳的自由膨胀并导致尾缘附近的压缩。在宇宙射线密度增加的过程中，还得出了宇宙射线密度向东北方向的空间梯度，这表明后缘附近的加热中心位于地球东北。这是最好的例子，表明观察高能宇宙射线为我们提供了只能从宇宙射线测量中得出的信息，以观察性地约束了日冕物质抛射与周围环境相互作用的三维宏观图太阳风，