Understanding the formation and eruption of sigmoidal structure through data-driven modeling of magnetic evolution in solar active region 13500

Abstract

We investigate the magnetic origin of the coronal mass ejection that occurred on 2023 November 28 at 19:50 UT from NOAA Active Region 13500 located near the solar disk center. The eruption was associated with an S-shaped sigmoidal structure formed by the inner active region (AR) polarities along a sheared polarity inversion line, while the outer polarities evolved through proper motions. During 2023 November 26–28, the AR exhibited a decrease in net magnetic flux, while progressively injecting magnetic helicity and energy into the corona toward the eruption onset, highlighting the key role of helicity injection in triggering eruptions. To simulate this magnetic evolution, we employed a data-driven magnetofrictional (MF) simulation starting 2.8 days prior to the eruption. The energy input for the model was constrained using the observed energy injection through an ad hoc parameter. The initial potential-field configuration gradually evolved into a sheared arcade and eventually developed into a twisted flux rope (FR) over the observed timescale. Proxy emission maps based on electric currents show remarkable morphological agreement between the simulated and observed sigmoidal structures. The average FR core twist increasingly builds up, leading the FR to initiate a slow-rise motion of the FR top from 50 Mm until its eruption onset at 80 Mm. Importantly, the ratio of the current-carrying to total relative helicity increased from 0.13 at the FR formation to 0.30 at eruption, when the FR core entered the torus-unstable regime, suggesting an association between torus instability and the threshold helicity ratio. These results demonstrate that data-driven MF simulations can successfully reproduce the evolving coronal magnetic configuration and may provide a robust tool for assessing the eruptive potential of ARs, particularly the helicity ratio.