Spectro-imagery of an active tornado-like prominence: Formation and evolution
Spectro-imagery of an active tornado-like prominence: Formation and evolution
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活跃的龙卷风突出物的光谱图像：形成和演化
DOI：
10.1051/0004-6361/202140976
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发表时间：
2021
影响因子：
6.5
通讯作者：
Barczynski K
中科院分区：
文献类型：
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作者：
Barczynski K
日冕中精细结构的动力学性质仍然是一个悬而未决的问题，包括龙卷风日冕中的旋转流动。太阳动力学观测站上的大气成像组件成像仪允许我们跟踪龙卷风状日冕的全球结构五个小时，而界面区域成像光谱仪和多通道减去双程光谱仪允许对其精细结构进行等离子体诊断。首先，在有倾角的磁绳磁力支撑结构中，观测到的等离子体旋转在概念上是可接受的吗？其次，在龙卷风状日冕中等离子体密度是如何分布的？方法对MG II谱线采用高斯拟合法，对Hα谱线采用平分线法，计算了视线速度和非热谱线宽度。利用一维非长余辉辐射输运理论模型，由Mg II谱线的积分强度和轮廓拟合方法确定了它们的电子密度。结果Hα、Mg II h和k谱线观测到的日冕整体结构符合DIPS磁场结构构型。在这两条直线上观察到的红移区和蓝移区的相干多普勒频移沿着快速变化的垂直和水平结构被检测到。然而，日冕顶部的龙卷风由多条流动相反的细线组成，这意味着逆流流动而不是旋转。令人惊讶的是，日冕顶部的电子密度可能比日冕内部的电子密度大(1011 cm−3)。结论我们认为龙卷风处于一种形成状态，第一阶段热等离子体冷却，随后形成的气泡泄漏阶段，沿长圈有大量横向流动的物质从紫外线日冕顶部向外延伸。日冕两侧如此长的磁力线的存在将阻止龙卷风般的日冕真正绕着它的轴旋转。
ContextThe dynamical nature of fine structures in prominences remains an open issue, including rotating flows in tornado prominences. While the Atmospheric Imaging Assembly imager aboard the Solar Dynamics Observatory allowed us to follow the global structure of a tornado-like prominence for five hours, the Interface Region Imaging Spectrograph, and the Multichannel Subtractive Double Pass spectrograph permitted to obtain plasma diagnostics of its fine structures.AimsWe aim to address two questions. Firstly, is the observed plasma rotation conceptually acceptable in a flux rope magnetic support configuration with dips? Secondly, how is the plasma density distributed in the tornado-like prominence?MethodsWe calculated line-of-sight velocities and non-thermal line widths using Gaussian fitting for Mg II lines and the bisector method for Hαline. We determined the electron density from Mg II line integrated intensities and profile fitting methods using 1D non-LTE radiative transfer theory models.ResultsThe global structure of the prominence observed in Hα, and Mg II h, and k line fits with a magnetic field structure configuration with dips. Coherent Doppler shifts in redshifted and blueshifted areas observed in both lines were detected along rapidly-changing vertical and horizontal structures. However, the tornado at the top of the prominence consists of multiple fine threads with opposite flows, suggesting counter-streaming flows rather than rotation. Surprisingly we found that the electron density at the top of the prominence could be larger (1011cm−3) than in the inner part of the prominence.ConclusionsWe suggest that the tornado is in a formation state with cooling of hot plasma in a first phase, and following that, a phase of leakage of the formed blobs with large transverse flows of material along long loops extended away from the UV prominence top. The existence of such long magnetic field lines on both sides of the prominence would stop the tornado-like prominence from really turning around its axis.