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Heating and cooling of coronal loops with turbulent suppression of parallel heat conduction

机译:加热和冷却冠状环与湍流抑制   平行热传导

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摘要

Using the "enthalpy-based thermal evolution of loops" (EBTEL) model, weinvestigate the hydrodynamics of the plasma in a flaring coronal loop in whichheat conduction is limited by turbulent scattering of the electrons thattransport the thermal heat flux. The EBTEL equations are solved analytically ineach of the two (conduction-dominated and radiation-dominated) cooling phases.Comparison of the results with typical observed cooling times in solar flaresshows that the turbulent mean free-path $\lambda_T$ lies in a rangecorresponding to a regime in which classical (collision-dominated) conductionplays at most a limited role. We also consider the magnitude and duration ofthe heat input that is necessary to account for the enhanced values oftemperature and density at the beginning of the cooling phase and for theobserved cooling times. We find through numerical modeling that in order toproduce a peak temperature $\simeq 1.5 \times 10^7$~K and a 200~s cooling timeconsistent with observations, the flare heating profile must extend over asignificant period of time; in particular, its lingering role must be takeninto consideration in any description of the cooling phase. Comparison withobservationally-inferred values of post-flare loop temperatures, densities, andcooling times thus leads to useful constraints on both the magnitude andduration of the magnetic energy release in the loop, as well as on the value ofthe turbulent mean free-path $\lambda_T$.
机译:使用“基于焓的环的热演化”(EBTEL)模型,我们研究了扩口日冕环中等离子体的流体动力学,在该环中,热传导受到传输热通量的电子的湍流散射的限制。 EBTEL方程在两个(传导主导和辐射主导)冷却阶段均经过解析求解,结果与典型的太阳耀斑冷却时间的比较表明,湍流平均自由程$ \ lambda_T $处于与经典(冲突为主)传导最多发挥有限作用的体制。我们还考虑了热量输入的大小和持续时间,这是考虑到冷却阶段开始时温度和密度的增加值以及观察到的冷却时间所必需的。通过数值模拟我们发现,为了产生峰值温度$ \ simeq 1.5 \乘以10 ^ 7 $〜K和200〜s的冷却时间与观测值一致,火炬的加热曲线必须在相当长的一段时间内延伸。特别地,在冷却阶段的任何描述中都必须考虑到其挥之不去的作用。因此,与观测到的耀斑后回路温度,密度和冷却时间的值进行比较,将对回路中释放的磁能的大小和持续时间以及湍流平均自由程$ \ lambda_T的值产生有用的限制$。

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