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arXiv 1003.1255astro-ph.SR
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连接太阳宁静表面和炽热外层大气的小磁环

Small magnetic loops connecting the quiet surface and the hot outer atmosphere of the Sun

M. J. Martinez Gonzalez, R. Manso Sainz, A. Asensio Ramos, L. R. Bellot Rubio

摘要:

太阳黑子是太阳磁场最壮观的表现形式,然而,在太阳活动周期的任何时候,99%的太阳表面都保持“安静”。然而,安静的太阳并非没有磁场;它们在较小的空间尺度上组织起来,并且演化得相对较快,这使得它们难以被检测到。因此,虽然广泛的安静的太阳磁场是太阳外层大气均匀、稳定加热的自然驱动力,但由于缺乏观测证据,尚不清楚所涉及的物理过程。我们报告的拓扑结构和动力学的磁场在太阳非常安静的地区从分光偏振观测的日出卫星,显示连续注入的磁通量与一个组织良好的拓扑结构的欧米茄环从太阳表面以下到上层。在第一阶段,当环穿过光球层时,它有一个扁平的(像订书钉一样的)几何形状和$\sim3$ km/s的平均速度上升。当线圈穿过最低温度区域时,足点处的磁场几乎变成垂直的,并且线圈拓扑类似于一个势场。色球层高度的平均上升速度为$\sim12$ km/s。色球层下边界的这些小尺度环的能量输入率(至少)为1.4x10^6-2.2x10^7 erg cm-2 s-1。我们的研究结果为太阳磁场作为一个多尺度系统提供了经验证据,其中小尺度低通量磁场起着至关重要的作用,至少与活动区域一样重要,耦合太阳大气的不同层,并且是色球和日冕加热模型的重要组成部分。

英文摘要:

Sunspots are the most spectacular manifestation of solar magnetism, yet, 99% of the solar surface remains 'quiet' at any time of the solar cycle. The quiet sun is not void of magnetic fields, though; they are organized at smaller spatial scales and evolve relatively fast, which makes them difficult to detect. Thus, although extensive quiet Sun magnetism would be a natural driver to a uniform, steady heating of the outer solar atmosphere, it is not clear what the physical processes involved would be due to lack of observational evidence. We report the topology and dynamics of the magnetic field in very quiet regions of the Sun from spectropolarimetric observations of the Hinode satellite, showing a continuous injection of magnetic flux with a well organized topology of Omega-loop from below the solar surface into the upper layers. At first stages, when the loop travels across the photosphere, it has a flattened (staple-like) geometry and a mean velocity ascent of $\sim3$ km/s. When the loop crosses the minimum temperature region, the magnetic fields at the footpoints become almost vertical and the loop topology ressembles a potential field. The mean ascent velocity at chromospheric height is $\sim12$ km/s. The energy input rate of these small-scale loops in the lower boundary of the chromosphere is (at least) of 1.4x10^6-2.2x10^7 erg cm-2 s-1. Our findings provide empirical evidence for solar magnetism as a multi-scale system, in which small-scale low-flux magnetism plays a crucial role, at least as important as active regions, coupling different layers of the solar atmosphere and being an important ingredient for chromospheric and coronal heating models.

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