Observing Current Sheet Formation Forced by Non-radial Rotating Motion of Mini-filaments
Observing Current Sheet Formation Forced by Non-radial Rotating Motion of Mini-filaments
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DOI：
10.3847/1538-4357/ab24ce
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发表时间：
2019-07
期刊：
影响因子：
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通讯作者：
Hechao Chen;Jiayan Yang;Yadan Duan;Kaifan Ji
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文献类型：
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作者：
Hechao Chen;Jiayan Yang;Yadan Duan;Kaifan Ji
在本文中，我们研究了NOAA活跃区12494附近的两个外部强迫磁重联事件对它们的电流片（CS）形成的影响。在这两种情况下，微型细丝和其他预先存在的磁场之间都发生了小规模的重联。最初，微丝由于失去平衡而发生明显的非径向旋转运动。随着微丝的顺时针/逆时针旋转，微丝的轴向通量逐渐挤压反平行的环境场，形成x形结构。随着挤压效应的增强，CS区逐渐形成，长度逐渐增加，温度在1.8 MK左右。随后，清晰的尖峰区、等离子体加热（~ 5 MK）和新的磁性结构依次出现。最后，由于外部重新连接的参与，微型细丝以复杂的方式爆发。在多波长成像观测的基础上，仔细分析了CS区的表观厚度/长度、温度/发射及其相关的等离子体流。它们的重连率大致估计为0.01-0.06和0.01-0.02。特别是，在Event1中检测到高速等离子体抛射链和一组重连接的场线，这意味着在其CS区域内开始出现撕裂模式不稳定。这些观察结果表明，细丝的非径向旋转运动可以作为驱动重联的外部流动，也为小规模磁重联过程中CS形成提供了基本场景。
In this paper, we study two externally forced magnetic reconnection events near NOAA active region 12494 for their current sheet (CS) formation. In both events, small-scale reconnection happened between mini-filaments and other preexisting magnetic fields. Initially, mini-filaments underwent obvious non-radial rotating motion due to their loss of equilibrium. With their clockwise/anti-clockwise rotation, the axial fluxes of the mini-filaments slowly came to squeeze the anti-parallel ambient fields, leading to an X-shaped structure. As the squeezing effect strengthened, CS regions gradually formed and grew in length, with a temperature around 1.8 MK. Afterward, clear cusp regions, plasma heating (∼5 MK), and newborn magnetic structures came to be in sequence. Finally, mini-filaments erupted in a complex fashion due to the involvement of external reconnection. Based on the multiwavelength imaging observations, the apparent thickness/length, temperature/emission of the CS regions and their related plasma flows are carefully analyzed. Their reconnection rates are roughly estimated as 0.01–0.06 and 0.01–0.02. In particular, a chain of high-speed plasmoid ejections was detected along with a set of the reconnected field lines in Event1, implying the onset of tearing-mode instability inside its CS region. These observations indicate that non-radial rotating motion of filaments can serve as external flows to drive reconnection, and also provide a basic scenario of CS formation within small-scale magnetic reconnetion processes.