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arXiv 1406.0404astro-ph.SR
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加热太阳日冕环的基于级联的机制:对观测的检验

Parallel-cascade-based mechanisms for heating solar coronal loops: test against observations

Bo Li, Haixia Xie, Xing Li, Li-Dong Xia

摘要:

太阳日冕环的加热是日冕加热问题的核心。鉴于快速太阳风的起源已经被追踪到具有过渡区甚至色球温度的大气层,因此值得尝试解决所提出的为太阳风提供基底加热的机制是否也适用于日冕环。我们扩展的循环研究的基础上,一个经典的平行级联的情况下,最初提出的太阳风的背景下,考虑到环膨胀的影响,并进行参数研究,直接对比计算的环密度和电子温度与那些测量的TRACE和YOHKOH/SXT。这种比较得出的结论是,在观测上受SUMER测量值约束的波振幅下,虽然计算出的循环可能占SXT循环的很大一部分,但与TRACE循环相比,它们似乎太热了。降低波的振幅并不能解决这个矛盾,引入磁扭曲将使比较更不可取。我们的结论是,纳米耀斑加热方案更好地解释了紫外线循环,而基于双折射的稳定加热机制可能在工作中加热一小部分软X射线循环。

英文摘要:

The heating of solar coronal loops is at the center of the problem of coronal heating. Given that the origin of the fast solar wind has been tracked down to atmospheric layers with transition region or even chromospheric temperatures, it is worthy attempting to address whether the mechanisms proposed to provide the basal heating of the solar wind apply to coronal loops as well. We extend the loop studies based on a classical parallel-cascade scenario originally proposed in the solar wind context by considering the effects of loop expansion, and perform a parametric study to directly contrast the computed loop densities and electron temperatures with those measured by TRACE and YOHKOH/SXT. This comparison yields that with the wave amplitudes observationally constrained by SUMER measurements, while the computed loops may account for a significant fraction of SXT loops, they seem too hot when compared with TRACE loops. Lowering the wave amplitudes does not solve this discrepancy, introducing magnetic twist will make the comparison even less desirable. We conclude that the nanoflare heating scenario better explains ultraviolet loops, while turbulence-based steady heating mechanisms may be at work in heating a fraction of soft X-ray loops.

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