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arXiv 1703.02808astro-ph.SR
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三维模拟中日冕加热事件的识别

Identification of coronal heating events in 3D simulations

Charalambos Kanella, Boris V. Gudiksen

摘要:

太阳日冕加热问题自1939年以来一直是一个悬而未决的问题。一个提出的模型的运输和释放的机械能产生的子光球层和光球是nanoflare模型,结合欧姆加热,通过磁重联释放一部分的能量存储在磁场中。验证这个模型的问题是,我们不能解决观测上的小尺度事件。耀斑的可观测特征的直方图,显示幂律行为,能量释放率,大小和总能量。根据能量释放的幂律指数,纳米耀斑可能是日冕加热的重要候选者;我们试图找到这个指数。在本文中,我们采用了数值程序Bifrost产生的3D-MHD模拟,和一种新的技术来识别在特定时刻的3D加热事件。我们探索的量是焦耳加热,这是明确相关的磁重联,因为依赖于旋度的磁场。我们能够在特定快照的卷$24 \times 24 \times 9.5 \ \textrm{Mm}^3$(即$768 \times 786 \times 331$网格单元)中识别4136个事件。我们发现每秒释放的能量的幂律斜率,和两个幂律斜率的确定的体积。所识别的能量事件并不代表所有释放的能量,但是在所识别的事件中,最大事件的总能量主导能量释放。大部分的能量释放发生在较低的日冕,而加热随着高度下降。我们发现,一个特定的识别方法,大事件可以分解成较小的,但在总的确定的能量释放的代价。不能被识别为事件的能量释放倾向于低能量释放机制。

英文摘要:

The solar coronal heating problem is an open question since 1939. One proposed model for the transport and release of mechanical energy generated in the sub-phorospheric layers and photosphere is the nanoflare model that incorporates Ohmic heating which releases a part of the energy stored in the magnetic field via magnetic reconnection. The problem with the verification of this model is that we cannot resolve observationally small scale events. Histograms of observable characteristics of flares, show powerlaw behavior, for both energy release rate, size and total energy. Depending on the powerlaw index of the energy release, nanoflares might be an important candidate for coronal heating; we seek to find that index. In this paper, we employ a numerical 3D-MHD simulation produced by the numerical code Bifrost, and a new technique to identify the 3D heating events at a specific instant. The quantity we explore is the Joule heating, which is explicitly correlated with the magnetic reconnection because depends on the curl of the magnetic field. We are able to identify 4136 events in a volume $24 \times 24 \times 9.5 \ \textrm{Mm}^3$ (i.e. $768 \times 786 \times 331$ grid cells) of a specific snapshot. We find a powerlaw slope of the released energy per second, and two powerlaw slopes of the identified volume. The identified energy events do not represent all the released energy, but of the identified events, the total energy of the largest events dominate the energy release. Most of the energy release happens in the lower corona, while heating drops with height. We find that with a specific identification method that large events can be resolved into smaller ones, but at the expense of the total identified energy releases. The energy release which cannot be identified as an event favours a low energy release mechanism.

机构、总结、中文摘要均由AI分析而来,可能存在错误,请以论文正文为准。

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