arXivDaily arXiv每日学术速递 周一至周五更新
arXiv 2007.14648astro-ph.SRphysics.plasm-phphysics.space-ph
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湍流日冕中的射电回波和太阳漂移对射电爆发的模拟

Radio Echo in the Turbulent Corona and Simulations of Solar Drift-Pair Radio Bursts

Alexey A. Kuznetsov, Nicolina Chrysaphi, Eduard P. Kontar, Galina Motorina

摘要:

漂移对爆发是一种不寻常的太阳低频射电辐射类型,它在动态光谱中表现为两个平行的漂移亮条纹。最近的成像光谱观测允许在源的大小,位置和演变方面的漂移对的定量表征。在这里,漂移对参数进行了定性分析,并与新发展的Monte Carlo射线追踪技术模拟无线电波传播的非均匀各向异性湍流日冕。结果表明,漂移对爆发可以形成由于折射和散射过程的组合,与拖尾分量是湍流反射(湍流无线电回波)的结果。漂移对爆发的形成需要与III型爆发中的等离子体密度波动水平相当的各向异性散射,但在内部湍流尺度具有更强的各向异性。各向异性的无线电波散射模型可以定量再现漂移对突发的关键属性:在给定频率下的表观源大小及其随时间的增加,源质心位置的平行运动,以及突发分量之间的延迟。拖尾分量被发现是几乎同空间和以下的主要组成部分。模拟结果表明,漂移对爆发可能会被观察到更接近磁盘中心和低于100 MHz,由于自由的吸收和散射的影响。漂移对的激发器与哨声传播包一致,这为诊断等离子体湍流和无线电发射机制提供了一种有趣的方法。

英文摘要:

Drift-pair bursts are an unusual type of solar low-frequency radio emission, which appear in the dynamic spectra as two parallel drifting bright stripes separated in time. Recent imaging spectroscopy observations allowed for the quantitative characterization of the drifting pairs in terms of source size, position, and evolution. Here, the drift-pair parameters are qualitatively analyzed and compared with the newly-developed Monte Carlo ray-tracing technique simulating radio-wave propagation in the inhomogeneous anisotropic turbulent solar corona. The results suggest that the drift-pair bursts can be formed due to a combination of the refraction and scattering processes, with the trailing component being the result of turbulent reflection (turbulent radio echo). The formation of drift-pair bursts requires an anisotropic scattering with the level of plasma density fluctuations comparable to that in type III bursts, but with a stronger anisotropy at the inner turbulence scale. The anisotropic radio-wave scattering model can quantitatively reproduce the key properties of drift-pair bursts: the apparent source size and its increase with time at a given frequency, the parallel motion of the source centroid positions, and the delay between the burst components. The trailing component is found to be virtually co-spatial and following the main component. The simulations suggest that the drift-pair bursts are likely to be observed closer to the disk center and below 100 MHz due to the effects of free-free absorption and scattering. The exciter of drift-pairs is consistent with propagating packets of whistlers, allowing for a fascinating way to diagnose the plasma turbulence and the radio emission mechanism.

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