使用ARTEMIS/JLS和NRH进行高分辨率观测：IV。II型爆发锋附近尖峰状结构的成像光谱
High-resolution observations with ARTEMIS/JLS and the NRH: IV. Imaging spectroscopy of spike-like structures near the front of type-II bursts
摘要：
窄带爆发（尖峰）出现在动态频谱从微波到十米波频率。它们被认为是通过磁重联释放小尺度能量的表现。我们研究了尖峰状结构相对于II型爆发前沿的位置及其在爆发发射中的作用。我们使用高灵敏度，低噪声的动态光谱获得的声光分析仪（SAO）的ARTEMIS-JLS射电光谱仪，结合图像从Nançay射电日像仪（NRH），以研究尖峰状的爆发在2003年11月3日极端太阳事件的II型射电爆发的前面附近。动态光谱中的尖峰状发射通过高通时间滤波得到增强。我们在NRH图像中发现了一些尖峰。由于NRH的时间分辨率较低，在动态光谱中检测到的多个尖峰在图像中表现为单个结构。这些尖峰的平均大小约为200”，观测到的亮温为1.4-5.6x10^9K，对II型爆发锋的发射有重要贡献。与以前的研究IV型相关的尖峰，我们发现没有系统的位移之间的尖峰发射和尖峰之间的发射。在327.0兆赫，第二类发射位于约0.3 RSUN以上的预先存在的连续发射，这是位于0.1 RSUN以上的西翼。这项研究表明，钉状链沿II型爆发MHD冲击波阵面是不是一个扰动的II型发射，在IV型尖峰的情况下，但II型发射本身的表现。这些链的优势，加上缺乏孤立的结构或不规则的集群，指向某种形式的小规模磁重联，组织沿II型传播前线。
英文摘要：
Narrowband bursts (spikes) appear on dynamic spectra from microwave to decametric frequencies. They are believed to be manifestations of small-scale energy release through magnetic reconnection. We study the position of the spike-like structures relative to the front of type-II bursts and their role in the burst emission. We used high-sensitivity, low-noise dynamic spectra obtained with the acousto-optic analyzer (SAO) of the ARTEMIS-JLS radiospectrograph, in conjunction with images from the Nançay Radioheliograph (NRH) in order to study spike-like bursts near the front of a type-II radio burst during the November 3, 2003 extreme solar event. The spike-like emission in the dynamic spectrum was enhanced by means of high-pass-time filtering. We identified a number of spikes in the NRH images. Due to the lower temporal resolution of the NRH, multiple spikes detected in the dynamic spectrum appeared as single structures in the images. These spikes had an average size of ~200" and their observed brightness temperature was 1.4-5.6x10^9K, providing a significant contribution to the emission of the type-II burst front. At variance with a previous study on the type-IV associated spikes, we found no systematic displacement between the spike emission and the emission between spikes. At 327.0 MHz, the type II emission was located about 0.3 RSUN above the pre-existing continuum emission, which, was located 0.1 RSUN above the western limb. This study indicates that the spike-like chains aligned along the type II burst MHD shock front are not a perturbation of the type II emission, as in the case of type IV spikes, but a manifestation of the type II emission itself. The preponderance of these chains, together with the lack of isolated structures or irregular clusters, points towards some form of small-scale magnetic reconnection, organized along the type-II propagating front.
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