CEDAR: Radar and Optical Observations of Enhanced Ion Acoustic Lines and Associated Auroral Fine Structure

该项目的科学目标是结合雷达、光学和卫星数据，研究和表征具有一致极光精细结构的自然增强离子声学线（neial）的发生，并提供对其可能产生机制的见解。为了实现这一目标，该项目将利用地面成像仪和扑克平面非相干散射雷达（PFISR）对夜间极光电离层的普通体积观测。现场测量将由日本的“黎明”号卫星进行，该卫星将在接近磁场午夜的时候，在全天相机视场（FOV）内每晚经过一次。观测将在2009年初（1月中旬到4月初）的三个月落期间进行，其中一个月落期间将在2010年初进行。PFISR对neial的观测提出了关于它们与特定极光形式的关系的新问题。增强的返回被发现发生在紧靠薄极光弧结构的黑暗区域，并以阿尔芬速度或接近阿尔芬速度进行高度传播。它们也被发现发生在大尺度极光特征的极地边缘附近。最近的观测发现，neals与非常动态的、小规模的极光弧有关，表明阿尔芬加速的电子沉淀。PFISR数据中的neal与卫星和火箭观测到的宽带极低频（BBELF）波具有匹配的形态和重叠的参数。这些观测结果表明neial与BBELF和Alfven波之间存在联系。对NEIAL产生机制的理解是对非相干散射雷达领域有益的补充，部分原因是NEIAL的存在阻碍了从雷达光谱中导出等离子体参数的正常拟合程序的应用。此外，neal可以用作研究电离层中发生的过程的手段，否则无法从ISR数据中获得这些过程。如果neal可以与特定类型的波活动、不稳定性或电子分布联系起来，那么ISRs就提供了一种基于地面的方法来研究它们发生的时间和地点。

The scientific objective of this project is to combine radar, optical and satellite data to investigate and characterize the occurrence of Naturally Enhanced Ion Acoustic Lines (NEIALs) with coincident auroral fine structures and to provide insight to their possible generation mechanisms. To accomplish this goal, the project will make use of common-volume observations of the nighttime auroral ionosphere with ground-based imagers and the Poker Flat Incoherent Scatter Radar (PFISR). In situ measurements will be made by the Japanese Reimei satellite which will pass once per night, near magnetic midnight, within the all-sky camera field of view (FOV). The observations will take place during the three moon down periods in early 2009 (mid-January through early-April), and one of the moon down periods in early 2010. PFISR observations of NEIALs have raised new questions regarding their occurrence in relation to specific auroral forms. The enhanced returns were found to occur in the dark regions immediately adjacent to thin auroral arc structures and to have altitude propagation at or near the Alfven speed. They are also found to occur near the poleward edge of the large-scale auroral features. Recent observations have found NEIALs to be associated with very dynamic, small-scale auroral arcs, indicative of Alfvenically accelerated electron precipitation. NEIALs in the PFISR data are observed with matching morphology and overlapping parameters as are the broad-band extremely low-frequency (BBELF) waves that are seen with satellites and rockets. These observations suggest connections between NEIALs and BBELF and Alfven waves. The understanding of NEIAL generation mechanisms is a beneficial addition to the incoherent scatter radar community, partly because the presence of NEIALs prevents the application of the normal fitting procedure used to derive the plasma parameters from the radar spectra. Also, NEIALs can be used as a means to study processes occurring in the ionosphere that would not otherwise be obtainable from ISR data. If NEIALs can be linked to specific types of wave activity, instabilities, or electron distributions, then ISRs provide a ground-based method to study when and where they occur.