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Tracking the motion of a shock along a channel in the low solar corona
Astronomy & Astrophysics ( IF 6.5 ) Pub Date : 2024-04-08 , DOI: 10.1051/0004-6361/202348452 J. Rigney , P. T. Gallagher , G. Ramsay , J.G. Doyle , D.M. Long , O. Stepanyuk , K. Kozarev
Astronomy & Astrophysics ( IF 6.5 ) Pub Date : 2024-04-08 , DOI: 10.1051/0004-6361/202348452 J. Rigney , P. T. Gallagher , G. Ramsay , J.G. Doyle , D.M. Long , O. Stepanyuk , K. Kozarev
Context. Shock waves are excited by coronal mass ejections (CMEs) and large-scale extreme-ultraviolet (EUV) wave fronts and can result in low-frequency radio emission under certain coronal conditions.Aims. In this work, we investigate a moving source of low-frequency radio emission as a CME and an associated EUV wave front move along a channel of a lower density, magnetic field, and Alfvén speed in the solar corona.Methods. Observations from the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory, the Nançay Radio Heliograph (NRH), and the Irish Low Frequency Array (I-LOFAR) were analysed. Differential emission measure maps were generated to determine densities and Alfvén maps, and the kinematics of the EUV wave front was tracked using CorPITA. The radio sources’ positions and velocity were calculated from NRH images and I-LOFAR dynamic spectra.Results. The EUV wave expanded radially with a uniform velocity of ∼500 km s−1. However, the radio source was observed to be deflected and appeared to move along a channel of a lower Alfvén speed, abruptly slowing from 1700 km s−1 to 250 km s−1 as it entered a quiet-Sun region. A shock wave with an apparent radial velocity of > 420 km s−1 was determined from the drift rate of the associated Type II radio burst.Conclusions. The apparent motion of the radio source may have resulted from a wave front moving along a coronal wave guide or by different points along the wave front emitting at locations with favourable conditions for shock formation.
中文翻译：
跟踪低日冕中沿通道的冲击运动
语境。冲击波由日冕物质抛射 (CME) 和大规模极紫外 (EUV) 波前激发，在某些日冕条件下会导致低频射电发射。目标。在这项工作中，我们研究了日冕物质抛射和相关的 EUV 波前沿着日冕中密度、磁场和阿尔文速度较低的通道移动时低频无线电发射的移动源。方法。对太阳动力学天文台大气成像组件、南赛射电日光仪 (NRH) 和爱尔兰低频阵列 (I-LOFAR) 的观测结果进行了分析。生成差分发射测量图以确定密度和阿尔文图，并使用 CorPITA 跟踪 EUV 波前的运动学。无线电源的位置和速度是根据 NRH 图像和 I-LOFAR 动态频谱计算得出的。结果。 EUV 波以约 500 km s -1的均匀速度径向扩展。然而，观察到射电源发生了偏转，并且似乎沿着阿尔文速度较低的通道移动，当它进入安静的太阳区域时，速度突然从 1700 km s -1减慢到 250 km s -1 。根据相关 II 型射电暴的漂移率确定表观径向速度 > 420 km s -1的冲击波。结论。无线电源的表观运动可能是由于波前沿冠状波导移动或由沿波前的不同点在具有形成激波的有利条件的位置发射的结果造成的。
更新日期：2024-04-08
中文翻译：
跟踪低日冕中沿通道的冲击运动
语境。冲击波由日冕物质抛射 (CME) 和大规模极紫外 (EUV) 波前激发，在某些日冕条件下会导致低频射电发射。目标。在这项工作中，我们研究了日冕物质抛射和相关的 EUV 波前沿着日冕中密度、磁场和阿尔文速度较低的通道移动时低频无线电发射的移动源。方法。对太阳动力学天文台大气成像组件、南赛射电日光仪 (NRH) 和爱尔兰低频阵列 (I-LOFAR) 的观测结果进行了分析。生成差分发射测量图以确定密度和阿尔文图，并使用 CorPITA 跟踪 EUV 波前的运动学。无线电源的位置和速度是根据 NRH 图像和 I-LOFAR 动态频谱计算得出的。结果。 EUV 波以约 500 km s -1的均匀速度径向扩展。然而，观察到射电源发生了偏转，并且似乎沿着阿尔文速度较低的通道移动，当它进入安静的太阳区域时，速度突然从 1700 km s -1减慢到 250 km s -1 。根据相关 II 型射电暴的漂移率确定表观径向速度 > 420 km s -1的冲击波。结论。无线电源的表观运动可能是由于波前沿冠状波导移动或由沿波前的不同点在具有形成激波的有利条件的位置发射的结果造成的。
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