Morphology of the quiet Sun between 150 and 450 MHz as observed with the Nançay radioheliograph
Morphology of the quiet Sun between 150 and 450 MHz as observed with the Nançay radioheliograph
复制标题
使用 Nançay 射电日照仪观察到的 150 至 450 MHz 之间安静太阳的形态
DOI：
10.1051/0004-6361/201118163
复制
发表时间：
2012
影响因子：
6.5
通讯作者：
G. Chambe
中科院分区：
文献类型：
--
作者：
C. Mercier;G. Chambe
上下文自2004年最后一次升级以来，南赛射电日像仪（NRH）能够在150-450 MHz范围内产生可靠的安静太阳图像，这对应于低和中等日冕。这些图像优于以前获得的NRH或其他仪器在这个范围内，适合定量和系统的开发。目标。我们的目标是研究太阳大气层的无线电方面。我们的目标是专注于描述的形态和比较观察EUV和X射线范围内，并与磁结构。方法.我们使用了旋转孔径合成技术（适用于非时变对象）沿着与原始自校准程序和特定的反卷积算法（CLEAN的变体，包括尺度分析）。结果我们目前的结果，从无线电成像的安静的太阳与NRH。该分析在2004年至2011年的夏季（6月至8月）进行了约160天。我们确认并扩展了我们的第一个结果，这些结果是从一个小得多的数据样本中发布的。我们强调在这个频率范围内观察到的日冕的新方面，特别是日冕洞的存在比以前报道的暗通道在高频率。我们给出的例子，说明了复杂的日冕结构的形态所揭示的无线电成像，中心到肢体的影响（无线电掩星）和太阳周期的相位的变化。我们将我们的图像与大规模的日冕磁结构进行了比较。我们发现，在高频率下看到的暗冕洞和通道以及在低频率下看到的亮带似乎与特定类型的磁结构有关。结论.在这个频率范围内的详细无线电图像是一种新的工具，具有很高的潜力，用于调查低和中日冕，因为这些图像可以强调在其他波长下不可见的结构。在不久的将来，从NRH在周期上升部分的观测（从未在m/dcm波长观测到）以及从NRH和GMRT组合数据的合成图像中可以学到很多东西，这些数据将具有更好的分辨率。在第二步中，将感兴趣的是获得圆偏振图像（给出日冕磁场的诊断）和新一代仪器的图像，这将产生具有较短合成图像的详细图像，甚至快照图像，由此在较短的时间尺度上演变过程
Context. Since its last upgrading in 2004, the Nançay radioheliograph (NRH) is able to produce reliable images of the quiet Sun in the 150–450 MHz range, which corresponds to the low and medium corona. These images are better than those previously obtained with the NRH or other instruments in this range and are suitable for quantitative and systematic exploitation. Aims. We aim to study the radio aspects of the solar atmosphere. We aim to focuss on the description of the morphology and the comparisons with observations in EUV and X-ray ranges and with magnetic structures. Methods. We used the rotational aperture synthesis technique (suitable for non time-varying objects) along with an original selfcalibration procedure and a specific deconvolution algorithm (a variant of CLEAN that includes a scale analysis). Results. We present results from radio imaging of the quiet Sun with the NRH. The analysis was carried over about 160 days during the summers (June-August) from 2004 to 2011. We confirms and extend our first results, which were published from a much smaller data sample. We emphasize new aspects of the corona observed in this frequency range, in particular the existence of coronal holes darker than previously reported and dark channels at high frequencies. We give examples that illustrate the complex morphology of coronal structures as revealed by radio imaging, the center-to-limb effects (radio occultation) and the variation with the phase of the solar cycle. We compare our images with large-scale coronal magnetic structures. We show that dark coronal holes and channels seen at high frequencies and bright ribbons seen at low frequencies seem to be associated with particular types of magnetic structures. Conclusions. Detailed radio images in this frequency range are a new tool with high potential for investigating the low and middle corona, since these images can emphasize structures that are not (or much less) visible at other wavelengths. In the near future, there is much to learn from observations with NRH during the ascending part of the cycle (never observed at m/dcm wavelengths ) and from composite images of combined NRH and GMRT data, which will have a much better resolution. In a second step, it will be interesting to obtain circularly polarized images (giving a diagnostic of the coronal magnetic field) and images with new-generation instruments, which will yield detailed images with shorter synthesis or even snapshot images, from which processes evolving on shorter time scales