Imaging the May 2024 Extreme Aurora With Ionospheric Total Electron Content.

The continental United States is well instrumented with facilities for mid‐latitude upper atmosphere research that operate on a continuous basis. In addition, citizen scientists provide a wealth of information when unusual events occur. We combine ionospheric total electron content (TEC) data from distributed arrays of GNSS receivers, magnetometer chains, and auroral observations obtained by citizen scientists, to provide a detailed view of the intense auroral breakup and westward surge occurring at the peak of the 10–11 May 2024 extreme geomagnetic storm. Over a 20‐min interval, vertical TEC (vTEC) increased at unusually low latitude (∼45°) and rapidly expanded azimuthally across the continent. Individual receiver/satellite data sets indicate sharp bursts of greatly elevated of vTEC (∼50 TECu). Intense red aurora was co‐located with the leading edge of the equatorward and westward TEC enhancements, indicating that the large TEC enhancement was created by extremely intense low‐energy precipitation during the rapid substorm breakup. Plain Language Summary: For over 12 hr, the 10–11 May 2024 the extreme Gannon geomagnetic storm sent brilliant auroral displays into the night skies at mid and low latitudes around the world. Precipitating auroral electrons and protons ionize the upper atmosphere at 100–500 km altitude, increasing ionospheric total electron content (TEC). We use the perturbation of the signals received by the distributed array of navigation satellite receivers to map the intensification and spread of an extreme auroral event across the continental US. Photo and video observations of the auroral event contributed by citizen scientists indicate that the TEC enhancement closely matched the westward and equatorward expansion of strong red aurora. Coincident with the auroral breakup, sharp bursts of greatly elevated TEC were observed. Auroral breakup was accompanied by a bright red over green discrete auroral feature at the leading edge of the equatorward expansion of strong red aurora. Based on the direct auroral observations, we believe that the westward expansion of low‐energy electron precipitation is likely the driver of the large TEC enhancements observed during the event. Key Points: Total electron content (TEC) maps show the intensification and spread of the 11 May 2024 extreme auroral event across the continental US over a 20‐min intervalAll sky camera imagery indicates that the TEC enhancement closely matches the westward and equatorward expansion of strong red auroraCoincident with auroral breakup, individual receiver/satellite data sets show sharp bursts of greatly elevated TEC 50 TECu above background [ABSTRACT FROM AUTHOR]