论文标题
带有Murchison widefield阵列的带状型II型太阳能无线电爆发的成像 - 光谱镜检查
Imaging-spectroscopy of a band-split type II solar radio burst with the Murchison Widefield Array
论文作者
论文摘要
II型太阳能无线电爆发是由太阳喷发事件（例如冠状质量弹药（CMES））驱动的磁性水力动力学（MHD）引起的。通常，II型爆发的基本和谐波带被分为子带，通常被认为来自冲击的上游和下游区域。但是，这种解释仍未得到证实。在这里，我们介绍了II型无线电爆发带分解和其他精细结构的成像分析的结合结果，该结构由Murchison Widefield阵列（MWA）观察到2014年-Sep-28的太阳能动力学观测（SDO）/大气成像组件（AIA）的极端紫外线观测。 MWA可提供80-300 MHz范围内的成像 - 光谱镜，时间分辨率为0.5 s，频率分辨率为40 kHz。我们的分析表明，爆发是由活塞驱动的冲击引起的，驱动程序速度为$ \ sim $ 112 km s $^{ - 1} $和$ \ sim $ 580 km s $ s $^{ - 1} $的冲击速度。我们提供了罕见的证据表明，分裂是由电击的多个部分发射引起的（与上游/下游假设相反）。我们还检查了MWA图像中II型精细结构无线电源的小规模运动。我们建议，这种小规模的运动可能是由于冠状动脉湍流产生的无线电传播效应而产生的，而不是由于冲击位置的物理运动。我们提出了一种新型技术，该技术使用成像光谱直接确定湍流扰动的有效长度尺度，该湍流扰动的有效长度尺寸为1-2 mm。因此，对精细结构的系统和小规模运动的研究可能会在冲击和电晕的不同区域提供湍流的量度。
Type II solar radio bursts are caused by magnetohydrodynamics (MHD) shocks driven by solar eruptive events such as Coronal Mass Ejections (CMEs). Often both fundamental and harmonic bands of type II bursts are split into sub-bands, generally believed to be coming from upstream and downstream regions of the shock; however this explanation remains unconfirmed. Here we present combined results from imaging analysis of type II radio burst band-splitting and other fine structures, observed by the Murchison Widefield Array (MWA) and extreme ultraviolet observations from Solar Dynamics Observatory (SDO)/Atmospheric Imaging Assembly (AIA) on 2014-Sep-28. The MWA provides imaging-spectroscopy in the range of 80-300 MHz with a time resolution of 0.5 s and frequency resolution of 40 kHz. Our analysis shows that the burst was caused by a piston-driven shock with a driver speed of $\sim$112 km s$^{-1}$ and shock speed of $\sim$580 km s$^{-1}$. We provide rare evidence that band-splitting is caused by emission from multiple parts of the shock (as opposed to the upstream/downstream hypothesis). We also examine the small-scale motion of type II fine structure radio sources in MWA images. We suggest that this small-scale motion may arise due to radio propagation effects from coronal turbulence, and not because of the physical motion of the shock location. We present a novel technique that uses imaging spectroscopy to directly determine the effective length scale of turbulent density perturbations, which is found to be 1 - 2 Mm. The study of the systematic and small-scale motion of fine structures may therefore provide a measure of turbulence in different regions of the shock and corona.
