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.