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arXiv 0903.3880astro-ph.SR
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太阳活动区制约日冕加热的热线光谱观测

Spectroscopic Observations of Hot Lines Constraining Coronal Heating in Solar Active Regions

S. Patsourakos, J. A. Klimchuk

摘要:

对暖日冕环的EUV观测表明,它们是一束束未解析的链,被纳米耀斑脉冲加热到高温。然后等离子体将具有观察到的性质(例如,与静力平衡相比的过量密度)。如果这个解释是正确的,那么在正常耀斑之外应该有非常热的辐射。然而,据预测它会非常微弱。证明或反驳这一假设的一个关键因素是存在热的、非常微弱的等离子体,这些等离子体的数量应该是通过脉冲加热预测的。我们报告的第一个全面的光谱研究热等离子体在活跃地区。使用来自Hinode上的EIS光谱仪的数据来构建在1-5 MK温度范围内的静态活性区中的发射测量分布。分布是平坦的或缓慢增加到约3 MK,然后在更高的温度下迅速下降。我们表明,基于脉冲加热的活动区模型可以重现所观察到的EM分布相对较好。我们的结果提供了强有力的新证据,证明日冕加热本质上是脉冲性的。

英文摘要:

EUV observations of warm coronal loops suggest that they are bundles of unresolved strands that are heated impulsively to high temperatures by nanoflares. The plasma would then have the observed properties (e.g., excess density compared to static equilibrium) when it cools into the 1-2 MK range. If this interpretation is correct, then very hot emission should be present outside of proper flares. It is predicted to be vey faint, however. A critical element for proving or refuting this hypothesis is the existence of hot, very faint plasmas which should be at amounts predicted by impulsive heating. We report on the first comprehensive spectroscopic study of hot plasmas in active regions. Data from the EIS spectrometer on Hinode were used to construct emission measure distributions in quiescent active regions in the 1-5 MK temperature range. The distributions are flat or slowly increasing up to approximately 3 MK and then fall off rapidly at higher temperatures. We show that active region models based on impulsive heating can reproduce the observed EM distributions relatively well. Our results provide strong new evidence that coronal heating is impulsive in nature.

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