甚大阵VHF观测电离层TEC起伏谱分析新技术：从QP回波到MSTI
A New Technique for Spectral Analysis of Ionospheric TEC Fluctuations Observed with the Very Large Array VHF System: From QP Echoes to MSTIDs
摘要：
我们已经使用了一个相对较长的，连续的VHF观测明亮的宇宙射电源（天鹅座A）与甚大阵（VLA）通过夜间，中纬度电离层，以证明与此仪器可观察到的现象。在一篇配套论文中，我们证明了VLA可以检测到幅度<0.001 TECU的总电子含量（TEC）波动，并且可以测量精度约为0.0002 TECU/km的TEC梯度。我们详细介绍了两种互补的技术，用于产生这些TEC梯度测量的光谱分析。第一种是能够跟踪波长约为阵列一半大小（约20公里）或更多的单个波。这种技术是成功的检测和表征许多中等规模的旅行电离层扰动（MSTIDS）看到间歇性的整个夜晚，并已部分验证使用并发GPS测量。使用这种技术几乎在任何时候都可以看到较小的波，其中许多波的运动方向与检测到的MSTID相似。第二种技术允许检测和统计描述波长小至5公里的波群沿相似方向移动的特性。结合这两种谱技术的结果，我们发现了一类中等和小尺度的波，这可能是准周期（QP）回波已被观察到发生在零星的E（Es）层。我们发现这些波的两个不同的人群。一个人口的成员是一致的时间与MSTID和一致的E-F耦合不稳定性的Es层内产生的。其他种群似乎更受中性风的影响，类似于九州上空零星E实验发现的QP回波的主要类型（Yanhao等人，1998; Yamamoto等人，2005）。
英文摘要：
We have used a relatively long, contiguous VHF observation of a bright cosmic radio source (Cygnus A) with the Very Large Array (VLA) through the nighttime, midlatitude ionosphere to demonstrate the phenomena observable with this instrument. In a companion paper, we showed that the VLA can detect fluctuations in total electron content (TEC) with amplitudes of <0.001 TECU and can measure TEC gradients with a precision of about 0.0002 TECU/km. We detail two complementary techniques for producing spectral analysis of these TEC gradient measurements. The first is able to track individual waves with wavelengths of about half the size of the array (~20 km) or more. This technique was successful in detecting and characterizing many medium-scale traveling ionospheric disturbances (MSTIDs) seen intermittently throughout the night and has been partially validated using concurrent GPS measurements. Smaller waves are also seen with this technique at nearly all times, many of which move in similar directions as the detected MSTIDs. The second technique allows for the detection and statistical description of the properties of groups of waves moving in similar directions with wavelengths as small as 5 km. Combining the results of both spectral techniques, we found a class of intermediate and small scale waves which are likely the quasi-periodic (QP) echoes that have been observed to occur within sporadic-E (Es) layers. We find two distinct populations of these waves. The members of one population are coincident in time with MSTIDs and are consistent with being generated within Es layers by the E-F coupling instability. The other population seems more influenced by the neutral wind, similar to the predominant types of QP echoes found by the Sporadic-E Experiments over Kyushu (Fukao et al. 1998; Yamamoto et al. 2005).
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