Source positions of an interplanetary type III radio burst and anisotropic radio-wave scattering
Source positions of an interplanetary type III radio burst and anisotropic radio-wave scattering
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行星际III型射电暴的源位置和各向异性无线电波散射
DOI：
10.1051/0004-6361/202347185
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发表时间：
2023
影响因子：
6.5
通讯作者：
Chen X
中科院分区：
文献类型：
--
作者：
Chen X
行星际太阳射电III型爆发提供了远程研究和跟踪行星际介质中传播的高能电子的手段。由于缺乏直接的无线电源成像，已经开发了几种方法来根据天基观测确定源位置。此外，这些方法都没有考虑各向异性无线电波散射的传播效应，这会严重扭曲无线电波的轨迹，延迟其到达时间，并影响其表观特征。我们研究了帕克太阳探测器、太阳轨道飞行器、STEREO 和 Wind 同时观测到的行星际 III 型爆发的源位置和方向性，并将应用强度拟合和计时方法与具有各向异性密度涨落的无线电波传播的射线追踪模拟的结果进行比较。该模拟计算了光线的轨迹、不同观察地点的时间分布以及各种密度波动参数的表观特征。结果表明，观测到的源位置远离产生排放的位置，并且推导出的径向距离大于密度模型的预期。这表明视位置受到各向异性无线电波散射的影响，这导致视位置距太阳日心距离较大。如果确定源位置的方法不考虑靠近固有源位置的观察点处的无线电波传播路径和不完全散射，则它们可能会低估表观位置。
Interplanetary solar radio type III bursts provide the means to remotely study and track energetic electrons propagating in the interplanetary medium. Due to the lack of direct radio source imaging, several methods have been developed to determine the source positions from space-based observations. Moreover, none of the methods consider the propagation effects of anisotropic radio-wave scattering, which would strongly distort the trajectory of radio waves, delay their arrival times, and affect their apparent characteristics. We investigate the source positions and directivity of an interplanetary type III burst simultaneously observed by Parker Solar Probe, Solar Orbiter, STEREO, and Wind and we compare the results of applying the intensity fit and timing methods with ray-tracing simulations of radio-wave propagation with anisotropic density fluctuations. The simulation calculates the trajectories of the rays, their time profiles at different viewing sites, and the apparent characteristics for various density fluctuation parameters. The results indicate that the observed source positions are displaced away from the locations where emission is produced, and their deduced radial distances are larger than expected from density models. This suggests that the apparent position is affected by anisotropic radio-wave scattering, which leads to an apparent position at a larger heliocentric distance from the Sun. The methods to determine the source positions may underestimate the apparent positions if they do not consider the path of radio-wave propagation and incomplete scattering at a viewing site close to the intrinsic source position.