Analyzing the Sequence of Phases Leading to the Formation of the Active Region 13664, with Potential Carrington-like Characteristics

Abstract

Several recurrent X-class flares from Active Region (AR) 13664 triggered a severe G5-class geomagnetic storm between 2024 May 10 and 11. The morphology and compactness of this AR closely resemble the AR responsible for the famous Carrington Event of 1859. Although the induced geomagnetic currents produced a value of the Dst index, probably 1 order of magnitude weaker than that of the Carrington Event, the characteristics of AR 13664 warrant special attention. Understanding the mechanisms of magnetic field emergence and transformation in the solar atmosphere that lead to the formation of such an extensive, compact, and complex AR is crucial. Our analysis of the emerging flux and horizontal motions of the magnetic structures observed in the photosphere reveals the fundamental role of a sequence of emerging bipoles at the same latitude and longitude, followed by converging and shear motions. This temporal order of processes frequently invoked in magnetohydrodynamic models—emergence, converging motions, and shear motions—is critical for the storage of magnetic energy preceding strong solar eruptions that, under the right timing, location, and direction conditions, can trigger severe space weather events on Earth.