Blackstone Data from the May 11, 2024 Super Geomagnetic Storm

Fitacf data from the Blackstone SuperDARN radar on May 11, 2024. RST version 5.1 was used to create these files. Details about the file formats are maintained by the Data Analysis Working Group (https://superdarn.github.io/dawg/). Relevant file format naming conventions described below in the Files/Folders Description. A geomagnetic super storm, one of the largest in this solar cycle, was launched on 10 May 2024, producing spectacular auroral displays that could be observed across the continental United States (US) at middle and low latitudes. In this study, we focus on a brief 20-minute interval during the peak of the storm when intense low-energy precipitation and red aurora associated with a substorm auroral breakup were reported over the eastern sector of the US. This strong, low-energy precipitation event occurred in the field-of-view of the Blackstone (BKS) Super Dual Auroral Radar Network (SuperDARN) radar which observed strong near-range ionospheric backscatter across its field-of-view. We analyze the elevation and virtual height characteristics of the backscatter to show that the BKS radar observes F-region backscatter at unusually close ranges (<750 km) during the precipitation event interval. In addition, we note that BKS observes ionospheric backscatter over a broad range of elevation angles, including very high ones. It is not physically realistic that all the radio waves, launched over a broad range of elevation angles, refract to become perpendicular to the B-field. We therefore interpret that a sizable portion of this backscatter is produced by irregularities that are not field-aligned. These observations show that strong red aurora can have a significant impact on High Frequency (HF) radar operations. Finally, we discuss different mechanisms that could be generating the high-aspect angle irregularities producing coherent backscatter observed by SuperDARN.

本数据集为2024年5月11日采集自布莱克斯通（Blackstone）超级双极光雷达网（Super Dual Auroral Radar Network，缩写SuperDARN）雷达的拟合自相关函数（FitACF）数据，所有数据文件均通过RST 5.1版本软件生成。数据集文件格式的详细说明由数据分析工作组（Data Analysis Working Group，DAWG）维护，可参考链接：https://superdarn.github.io/dawg/。相关文件格式命名规范详见下文的“文件/文件夹说明”章节。
2024年5月10日爆发了本次太阳活动周期以来最强的地磁超级风暴之一，其引发的极光景观极为壮观，美国本土中低纬度地区均观测到此类极光现象。本研究聚焦于风暴峰值期间一段仅20分钟的时段，彼时美国东部区域被报道观测到强低能粒子沉降事件，以及伴随亚暴极光爆发（substorm auroral breakup）的红色极光。
此次强低能粒子沉降事件发生在布莱克斯通（代号BKS）超级双极光雷达网雷达的视场内，该雷达在其视场范围内捕捉到显著的近距电离层后向散射信号。我们通过分析后向散射信号的仰角与虚高特征，证实布莱克斯通雷达在该粒子沉降事件时段内，于异常近的距离范围（<750千米）内观测到电离层F区（F-region）后向散射信号。
此外，我们观测到布莱克斯通雷达在宽范围仰角区间内均能探测到电离层后向散射信号，其中包含极高仰角的信号。若所有从宽仰角发射的无线电波均经折射后与地磁场（B-field）垂直，则该情况在物理上并不具备现实合理性。因此我们认为，本次观测到的后向散射信号中有相当一部分来自于非场对齐（field-aligned）的电离层不规则体。
上述观测结果表明，强红色极光会对高频（High Frequency，HF）雷达的正常运行产生显著影响。最后，我们探讨了多种可能产生高方位角不规则体的机制，此类不规则体正是超级双极光雷达网观测到相干后向散射信号的成因。