Comparing Long-duration Gamma-Ray Flares and High-energy Solar Energetic Particles
Comparing Long-duration Gamma-Ray Flares and High-energy Solar Energetic Particles
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DOI：
10.3847/1538-4357/ab258f
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发表时间：
2019-05
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通讯作者：
G. A. Nolfo;A. Bruno;J. Ryan;Silvia Dalla;J. Giacalone;Ian G. Richardson;Ian G. Richardson;E. Christian;S. Stochaj;G. Bazilevskaya;M. Boezio;M. Martucci;V. Mikhailov;R. Munini
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作者：
G. A. Nolfo;A. Bruno;J. Ryan;Silvia Dalla;J. Giacalone;Ian G. Richardson;Ian G. Richardson;E. Christian;S. Stochaj;G. Bazilevskaya;M. Boezio;M. Martucci;V. Mikhailov;R. Munini
人们对康普顿伽马射线天文台、太阳极大任务和现在的费米太阳长持续伽马射线耀斑(LDGRF)的高能和持续发射的来源知之甚少。尽管费米大面积望远镜(LAT)已经发现了数十个具有LDGRF特征的耀斑，但由于能量极高和持续时间长，这种现象的本质一直是一个难以解释的问题。最高的能量发射通常被归因于≳300兆电子伏质子与周围物质相互作用产生的介子。延长的持续时间表明，粒子加速发生在日冕高处延伸的大体积上，要么来自大日冕环内的随机加速，要么来自日冕物质抛射驱动的冲击波的反向降水。有可能通过直接比较产生费米/LAT观测得出的γ射线发射的加速离子群的性质与物质-反物质探索和轻核天体物理航天器有效载荷在与费米探测到的与π有关的发射相对应的能量范围内测量的太阳高能粒子的特性来测试这些模型。对于其中的14个事件，我们比较了两个群体--空间中的SEP和太阳上相互作用的粒子--并从潜在来源的角度讨论了它们的含义。我们的分析表明，这两个质子数的相关性很差，它们的比值跨越了5个数量级以上，这表明激波加速粒子的反向沉淀不太可能是LDGRF发射的来源。
Little is known about the origin of the high-energy and sustained emission from solar long-duration gamma-ray flares (LDGRFs) identified with the Compton Gamma Ray Observatory, the Solar Maximum Mission, and now Fermi. Though the Fermi Large Area Telescope (LAT) has identified dozens of flares with LDGRF signatures, the nature of this phenomenon has been a challenge to explain due to both extreme energies and long durations. The highest-energy emission has generally been attributed to pion production from the interaction of ≳300 MeV protons with the ambient matter. The extended duration suggests that particle acceleration occurs over large volumes extending high in the corona, either from stochastic acceleration within large coronal loops or from back precipitation from coronal mass ejection–driven shocks. It is possible to test these models by making a direct comparison between the properties of the accelerated ion population producing the γ-ray emission derived from the Fermi/LAT observations and the characteristics of solar energetic particles (SEPs) measured by the Payload for Matter-Antimatter Exploration and Light Nuclei Astrophysics spacecraft in the energy range corresponding to the pion-related emission detected with Fermi. For 14 of these events, we compare the two populations—SEPs in space and the interacting particles at the Sun—and discuss the implications in terms of potential sources. Our analysis shows that the two proton numbers are poorly correlated, with their ratio spanning more than 5 orders of magnitude, suggesting that the back precipitation of shock-acceleration particles is unlikely to be the source of the LDGRF emission.