Abstract The extreme solar storm of 2024 May 10, during the 25th solar cycle, which recorded a symmetric H component index (Sym-H) reaching −500 nT, was the strongest since the 2003 Halloween storm. This event offered a unique opportunity for unprecedented multipoint observation of the complex interaction of interplanetary coronal mass ejections (ICMEs) from different vantage points. Utilizing NASA’s Wind, ACE, DSCOVR, THEMIS-C, STEREO-A, MMS, and ISRO’s recently launched Aditya-L1 spacecraft, we comprehensively investigated the spatiotemporal variations in interplanetary plasma and magnetic field parameters. Our study reveals large-scale quasi-steady magnetic reconnection within the interior of the ICME flux rope, possibly triggered by interactions between multiple ICMEs. A current sheet (CS) forms within the flux rope, enabling internal magnetic reconnection between concentric magnetic surfaces, which leads to a sharp reversal of the interplanetary magnetic field (IMF) B y component, as observed at the L1 point. Concurrently, reconnection exhaust and enhanced electron and ion fluxes were detected with the CS, extending over 200 R E (1.3 million kilometers) along the geocentric solar ecliptic y -direction. This finding sheds new light on the role of internal reconnection in ICME evolution, highlighting its pivotal role in modifying the morphology of the ICME magnetic structure and exerting severe space weather effects on Earth.
Biswas et al. (Mon,) studied this question.