A Model for Spectral and Compositional Variability at High Energies in Large, Gradual Solar Particle Events
A Model for Spectral and Compositional Variability at High Energies in Large, Gradual Solar Particle Events
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DOI：
10.1086/505106
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发表时间：
2006-08
期刊：
影响因子：
--
通讯作者：
A. Tylka;Martin A. Lee
中科院分区：
文献类型：
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作者：
A. Tylka;Martin A. Lee
由快速日冕物质抛射（CME）驱动的冲击通常被认为是大型渐进太阳高能粒子（SEP）事件的主要加速器。这一概念的一个关键挑战是这些事件的光谱和成分特征高度可变，每个核子的能量超过几十MeV。我们最近提出，这种可变性的结果从两个因素的相互作用：在冲击波法线角的冲击波从太阳向外移动的演变;和一个复合的种子人口，通常至少包括来自日冕（或太阳风）和来自耀斑的superthermals的superthermals。我们在这里提出了一个简单的分析实现这些想法。我们的计算半定量再现所观察到的变化，包括光谱形态和能量依赖性的Fe/O，3He/4He，和平均离子电荷的关键特征，在数据中的相关性是一致的。该模型预测的平均高能量Fe/O增强，证实了30年的观测，该模型还提供了一个定量解释的Breneman和斯通分馏效应，一个基本的，但以前无法解释的方面SEP现象。我们的计算必须支持未来的努力，结合现实的日冕物质抛射冲击模拟和粒子输运的严格治疗。日冕中的超热密度以及任意倾斜度冲击下注入过程的细节需要进一步研究。尽管如此，这些初步的结果提出了一个全面的框架来理解大部分（如果不是全部）大型SEP事件在冲击物理学方面的高能变异性的复杂性。
Shocks driven by fast coronal mass ejections (CMEs) are generally believed to be the dominant accelerators in large, gradual solar energetic particle (SEP) events. A key challenge for this notion has been the highly variable spectral and compositional characteristics of these events above a few tens of MeV per nucleon. We have recently proposed that this variability results from the interplay of two factors: evolution in the shock-normal angle as the shock moves outward from the Sun; and a compound seed population, typically comprising at least suprathermals from the corona (or solar wind) and suprathermals from flares. We present here a simple analytical implementation of these ideas. Our calculations semiquantitatively reproduce key features of the observed variability, including spectral morphologies and energy dependence in Fe/O, 3He/4He, and mean ionic charges, in ways that are consistent with correlations in the data. The model makes a prediction for the average high-energy Fe/O enhancement that is borne out by 30 years of observations; the model also provides a quantitative explanation for the Breneman & Stone fractionation effect, a fundamental but previously unexplained aspect of SEP phenomenology. Our calculations must be bolstered by future efforts incorporating realistic CME-shock simulations and a rigorous treatment of particle transport. Suprathermal densities in the corona, as well as details of the injection process at shocks of arbitrary obliquity, require further investigation. Nevertheless, these first results suggest a comprehensive framework for understanding the complexity of high-energy variability in terms of shock physics for most, if not all, large SEP events.