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arXiv 2201.06712astro-ph.SR
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高能粒子在日冕冲击波中加速的双幂律特征

Double-power-law feature of energetic particles accelerated at coronal shocks

Feiyu Yu, Xiangliang Kong, Fan Guo, Wenlong Liu, Zelong Jiang, Yao Chen, Joe Giacalone

摘要:

最近的观测表明,在许多大的太阳高能粒子(SEP)事件中,事件积分微分谱类似于双幂律。我们进行数值模拟的粒子加速在日冕冲击波传播通过一个流光状的磁场通过求解帕克输运方程,包括质子和较重的离子。我们发现,对于所有的离子物种的能谱集成在模拟域可以描述由一个双幂律,和断裂能量取决于离子的电荷质量比为$E_B \sim (Q/A)^α$,与$α$从0.16到1.2通过考虑不同的湍流光谱指数。我们认为,双幂律分布可能会出现的高能粒子从不同的源区域的加速率显着不同,由于粒子扩散的叠加的结果。高能粒子的扩散和混合也可以解释在某些SEP事件中观察到的高能量下Fe/O的增加。虽然进一步的混合过程可能会发生,我们的模拟表明,无论是幂律打破或翻转可以发生在太阳附近,并预测光谱形式变化显着沿冲击波阵面,这可能是即将到来的近太阳SEP测量帕克太阳探测器和太阳轨道器检查。

英文摘要:

Recent observations have shown that in many large solar energetic particle (SEP) events the event-integrated differential spectra resemble double power laws. We perform numerical modeling of particle acceleration at coronal shocks propagating through a streamer-like magnetic field by solving the Parker transport equation, including protons and heavier ions. We find that for all ion species the energy spectra integrated over the simulation domain can be described by a double power law, and the break energy depends on the ion charge-to-mass ratio as $E_B \sim (Q/A)^α$, with $α$ varying from 0.16 to 1.2 by considering different turbulence spectral indices. We suggest that the double power law distribution may emerge as a result of the superposition of energetic particles from different source regions where the acceleration rates differ significantly due to particle diffusion. The diffusion and mixing of energetic particles could also provide an explanation for the increase of Fe/O at high energies as observed in some SEP events. Although further mixing processes may occur, our simulations indicate that either power-law break or rollover can occur near the Sun and predict that the spectral forms vary significantly along the shock front, which may be examined by upcoming near-Sun SEP measurements from Parker Solar Probe and Solar Orbiter.

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