New Anisotropic Cosmic-Ray Enhancement (ACRE) Event on 5 November 2023 Due to Complex Heliospheric Conditions

IF 2.7 3区物理与天体物理 Q2 ASTRONOMY & ASTROPHYSICS

Solar Physics Pub Date : 2024-07-05 DOI:10.1007/s11207-024-02338-3

Agnieszka Gil, Eleanna Asvestari, Alexandar Mishev, Nicholas Larsen, Ilya Usoskin

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Abstract

The variability of galactic cosmic rays near Earth is nearly isotropic and driven by large-scale heliospheric modulation but rarely can very local anisotropic events be observed in low-energy cosmic rays. These anisotropic cosmic-ray enhancement (ACRE) events are related to interplanetary transients. Until now, two such events have been known. Here, we report the discovery of the third ACRE event observed as an increase of up to 6.4% in count rates of high- and midlatitude neutron monitors between ca. 09 – 14 UT on 5 November 2023 followed by a moderate Forbush decrease and a strong geomagnetic storm. This is the first known observation of ACRE in the midrigidity range of up to 8 GV. The anisotropy axis of ACRE was in the nearly anti-Sun direction. Modeling of the geomagnetic conditions implies that the observed increase was not caused by a storm-induced weakening of the geomagnetic shielding. As suggested by a detailed analysis and qualitative modeling using the EUHFORIA model, the ACRE event was likely produced by the scattering of cosmic rays on an intense interplanetary flux rope propagating north of the Earth and causing a glancing encounter. The forthcoming Forbush decrease was caused by an interplanetary coronal mass ejection that hit Earth centrally. A comprehensive analysis of the ACRE and complex heliospheric conditions is presented. However, a full quantitative modeling of such a complex event is not possible even with the most advanced models and calls for further developments.

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日光层条件复杂导致 2023 年 11 月 5 日发生新的各向异性宇宙射线增强（ACRE）事件

地球附近的银河宇宙射线的变异性几乎是各向同性的，由大尺度日光层调制驱动，但在低能宇宙射线中很少能观测到非常局部的各向异性事件。这些各向异性宇宙射线增强（ACRE）事件与行星际瞬变有关。到目前为止，已知有两个这样的事件。在这里，我们报告发现了第三个 ACRE 事件，即在 2023 年 11 月 5 日大约 09 - 14 UT 之间，高纬度和中纬度中子监测器的计数率增加了 6.4%，随后出现了中等程度的福布什下降和强烈的地磁暴。这是首次在高达 8 GV 的中刚度范围内观测到 ACRE。ACRE 的各向异性轴几乎位于反太阳方向。对地磁条件的建模表明，观测到的增加并不是风暴引起的地磁屏蔽减弱造成的。通过使用 EUHFORIA 模型进行的详细分析和定性建模表明，ACRE 事件很可能是由于宇宙射线散射到地球以北传播的强烈行星际通量绳上，并造成了一次擦肩而过。即将发生的福布什下降是由行星际日冕物质抛射造成的，它从中心撞击地球。本文对 ACRE 和复杂的日光层条件进行了全面分析。然而，即使使用最先进的模型也不可能对如此复杂的事件进行全面的定量建模，因此需要进一步开发。

本文章由计算机程序翻译，如有差异，请以英文原文为准。

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来源期刊

Solar Physics 地学天文-天文与天体物理

CiteScore

5.10

自引率

17.90%

发文量

146

审稿时长

1 months

期刊介绍： Solar Physics was founded in 1967 and is the principal journal for the publication of the results of fundamental research on the Sun. The journal treats all aspects of solar physics, ranging from the internal structure of the Sun and its evolution to the outer corona and solar wind in interplanetary space. Papers on solar-terrestrial physics and on stellar research are also published when their results have a direct bearing on our understanding of the Sun.