arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2005.10924astro-ph.SR
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离肢耀斑带的光谱特征和形成高度

Spectral Characteristics and Formation Height of Off-Limb Flare Ribbons

D. Kuridze, M. Mathioudakis, P. Heinzel, J. Koza, H. Morgan, R. Oliver, A. F. Kowalski, J. C. Allred

摘要:

耀斑带是太阳低层大气中耀斑能量耗散的明亮表现。我们首次报道了位于H $β$和Ca II 8542耀斑谱线边缘外的耀斑带的高分辨率成像光谱观测,并与辐射流体动力学模拟进行了详细的比较。使用瑞典太阳望远镜获得的X8.2级太阳耀斑SOL 2017 - 09 - 10 T16:06 UT的观测结果显示,位于耀斑环足点附近的H $β$线翼图像中有明亮的水平发射层。在H $β$机翼上观测到的带状物与名义上的光球边缘之间的视分离约为300 - 500公里。Ca II 8542的翼线图像显示了位于翼边缘的更微弱的带状辐射,与翼没有明显的分离。用RADYN模式研究了耀斑大气的合成谱线廓线,与观测结果符合较好。模拟结果表明,朝向临边,视线基本上是相对于垂直方向倾斜,燃烧的大气模型再现了高对比度的离临边H $β$带和他们的显着海拔以上的光球。在Ca II 8542的翼线图像中,带状物位于太阳低层大气的更深处,对比度较低。电子束能量的高度沉积与强度贡献函数的比较表明,H $β$线翼强度可以作为太阳低层大气耀斑能量沉积的有效示踪剂

英文摘要:

Flare ribbons are bright manifestations of flare energy dissipation in the lower solar atmosphere. For the first time, we report on high-resolution imaging spectroscopy observations of flare ribbons situated off-limb in the H$β$ and Ca II 8542 Å lines and make a detailed comparison with radiative hydrodynamic simulations. Observations of the X8.2-class solar flare SOL2017-09-10T16:06 UT obtained with the Swedish Solar Telescope reveal bright horizontal emission layers in H$β$ line wing images located near the footpoints of the flare loops. The apparent separation between the ribbon observed in the H$β$ wing and the nominal photospheric limb is about 300 - 500 km. The Ca II 8542 Å line wing images show much fainter ribbon emissions located right on the edge of the limb, without clear separation from the limb. RADYN models are used to investigate synthetic spectral line profiles for the flaring atmosphere, and good agreement is found with the observations. The simulations show that, towards the limb, where the line of sight is substantially oblique with respect to the vertical direction, the flaring atmosphere model reproduces the high contrast of the off-limb H$β$ ribbons and their significant elevation above the photosphere. The ribbons in the Ca II 8542 Å line wing images are located deeper in the lower solar atmosphere with a lower contrast. A comparison of the height deposition of electron beam energy and the intensity contribution function shows that the H$β$ line wing intensities can be an useful tracer of flare energy deposition in the lower solar atmosphere

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