Global Energetics of Solar Flares. VIII. The Low-energy Cutoff
Global Energetics of Solar Flares. VIII. The Low-energy Cutoff
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DOI：
10.3847/1538-4357/ab2cd4
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发表时间：
2019-06
期刊：
影响因子：
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通讯作者：
M. Aschwanden;E. P. Kontar;N. Jeffrey
中科院分区：
文献类型：
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作者：
M. Aschwanden;E. P. Kontar;N. Jeffrey
太阳耀斑物理学中的一个关键问题是确定低能截止值：这个值决定了非热电子的能量，从而决定了耀斑能量学。我们讨论了不同的方法来确定加速电子谱中的低能截止：（i）总电子数模型，（ii）飞行时间模型（基于飞行时间和碰撞偏转时间的等效性），（iii）Kontar等人的暖靶模型，以及（iv）热分量和非热分量之间的光谱交叉的模型。我们发现，前三个模型是一致的低能量截止的平均值为1.10 keV，而交叉模型提供了一个上限的低能量截止的平均值为1.21 keV。结合前三个模型，我们发现太阳耀斑中非热能与耗散磁能之比的平均值为qE = 0.57 ± 0.08，这与早期基于热目标模型的简化近似的研究结果（qE = 0.51 ± 0.17）相一致。这一研究证实了三种不同低能截止模型在计算非热耀斑能量时的自洽性。
One of the key problems in solar flare physics is the determination of the low-energy cut-off: the value that determines the energy of nonthermal electrons and hence flare energetics. We discuss different approaches to determine the low-energy cut-off in the spectrum of accelerated electrons: (i) the total electron number model, (ii) the time-of-flight model (based on the equivalence of the time-of-flight and the collisional deflection time), (iii) the warm target model of Kontar et al., and (iv) the model of the spectral cross-over between thermal and nonthermal components. We find that the first three models are consistent with a low-energy cutoff with a mean value of ≈10 keV, while the cross-over model provides an upper limit for the low-energy cutoff with a mean value of ≈21 keV. Combining the first three models we find that the ratio of the nonthermal energy to the dissipated magnetic energy in solar flares has a mean value of qE = 0.57 ± 0.08, which is consistent with an earlier study based on the simplified approximation of the warm target model alone (qE = 0.51 ± 0.17). This study corroborates the self-consistency between three different low-energy cutoff models in the calculation of nonthermal flare energies.