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Ionospheric irregularities observed during the Galactic and Extra‐galactic All‐sky MWA (GLEAM) survey
Radio Science ( IF 1.6 ) Pub Date : 2020-09-22 , DOI: 10.1029/2020rs007106
J. F. Helmboldt 1 , N. Hurley‐Walker 2
Affiliation  

Nearly 200 hours of observing with the Murchison Widefield Array (MWA) radio telescope during the Galactic and Extra‐galactic All‐sky MWA (GLEAM) survey were used to assemble images of ionospheric structure. These images cover a nearly 50°‐wide area on the sky at a cadence of 10 minutes over many 5‐7 hours‐long observing runs. They are generated by tracking the apparent motions of ~200‐‐800 cosmic radio sources caused by changes in the transverse gradient of the ionospheric total electron content. Spectral analysis of these images revealed that the dataset was dominated by three distinct signatures. The first is consistent with field‐aligned structures within the topside ionosphere/lower plasmasphere previously imaged with the MWA. The second are structures that are relatively large and aligned nearly east/west. Regional weather data implies that these are preferentially detected when there is a noticeable shear within the sub‐tropical jet stream, which passes near the MWA. This suggests that this signature may be related to gravity waves launched by jet stream shear. The final signature is consistent with the properties of so‐call electro‐buoyancy waves that are known to occur at midlatitudes at night. Detections of these were more common when regional sporadic‐E (ES) was present, supporting a proposed connection between these waves and polarization electric fields that may arise within ES. We discuss the implications for future observations with the Square Kilometer Array.

中文翻译:

在银河和银河外全天MWA(GLEAM)调查中观察到的电离层不规则

在银河系和银河系外星空MWA(GLEAM)勘测中,用Murchison宽场阵列(MWA)射电望远镜进行了近200小时的观测,以收集电离层结构的图像。这些图像在5到7个小时的长时间观察运行中,以10分钟的节奏覆盖了近50°的天空区域。它们是通过跟踪约200-800个宇宙无线电源的视运动而产生的,这些运动是由电离层总电子含量的横向梯度变化引起的。这些图像的光谱分析表明,该数据集由三个不同的特征所主导。第一个与先前用MWA成像的顶电离层/下部等离子层内的场对准结构一致。第二个是相对较大的结构,几乎向东/向西对齐。区域天气数据表明,当在靠近MWA的亚热带急流中出现明显剪切时,优先检测到这些。这表明该特征可能与喷射流剪切产生的重力波有关。最终的特征与已知在夜间中纬度发生的所谓电浮力波的特性一致。在区域性零星E(È小号)存在,支持这些波和极化电场中可能出现的之间的连接提出ê小号。我们将讨论平方千米阵列对未来观测的影响。
更新日期:2020-09-22
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