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arXiv 2103.13499astro-ph.SR
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太阳日冕加热中基本事件的能量学和三维结构

Energetics and 3-D Structure of Elementary Events in Solar Coronal Heating

G. Einaudi, R. B. Dahlburg, I. Ugarte-Urra, J. W. Reep, A. F. Rappazzo, M. Velli

摘要:

帕克(Parker,1972)首先提出日冕加热是光球流缠绕日冕磁场线所产生的能量流的必然结果。在本文中,我们将讨论如何修改这个模型已被随后的数值模拟,特别是概述了帕克和“基本事件”,这里定义为小规模的空间和时间隔离的加热事件所产生的连续形成和耗散的场对齐的电流片在日冕循环中引入的“nanoflares”之间的实质性差异。本文采用HYPERION程序对三维可压缩磁流体动力学方程进行了数值模拟。我们使用两种聚类算法来研究模拟基本事件的属性:基于密度的空间聚类应用程序与噪声(DBSCAN)技术的IDL实现;和我们自己的物理距离聚类(PDC)算法。我们识别和跟踪基本加热事件的时间,无论是在温度和焦耳加热空间。对于每个事件,我们都会描述其属性,例如:密度、温度、体积、纵横比、长度、厚度、持续时间和能量。事件的能量在$10^{18}-10^{21}$尔格范围内,持续时间短于100秒。一些事件持续长达200秒,释放的能量高达$10^{23}$尔格。虽然高温通常位于通量管顶点,但电流一直延伸到足点。因此,一个单一的基本事件目前无法检测。观测到的辐射是由于环内空间和时间上随机分布的许多基本事件的叠加。

英文摘要:

Parker (1972) first proposed that coronal heating was the necessary outcome of an energy flux caused by the tangling of coronal magnetic field lines by photospheric flows. In this paper we discuss how this model has been modified by subsequent numerical simulations outlining in particular the substantial differences between the "nanoflares" introduced by Parker and "elementary events", defined here as small-scale spatially and temporally isolated heating events resulting from the continuous formation and dissipation of field-aligned current sheets within a coronal loop. We present numerical simulations of the compressible 3-D MHD equations using the HYPERION code. We use two clustering algorithms to investigate the properties of the simulated elementary events: an IDL implementation of a Density-Based Spatial Clustering of Applications with Noise (DBSCAN) technique; and our own Physical Distance Clustering (PDC) algorithm. We identify and track elementary heating events in time, both in temperature and in Joule heating space. For every event we characterize properties such as: density, temperature, volume, aspect ratio, length, thickness, duration and energy. The energies of the events are in the range $10^{18}-10^{21}$ ergs, with durations shorter than 100 seconds. A few events last up to 200 seconds and release energies up to $10^{23}$ ergs. While high temperature are typically located at the flux tube apex, the currents extend all the way to the footpoints. Hence a single elementary event cannot at present be detected. The observed emission is due to the superposition of many elementary events distributed randomly in space and time within the loop.

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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