Speaker
Description
Understanding the causative mechanisms behind solar eruptions and solar energetic particle events is crucial for space weather forecasting. However, although numerous models have been proposed regarding the relationship between the magnetic fields of active regions and solar eruptions, the structure and parameters of the magnetic fields that govern these events remain unclear, which still hinders the accurate forecasting of space weather events. We have recently developed a new prediction scheme for large flares, known as the κ-scheme, based on MHD instability theory (Kusano et al. 2020, Science). The κ-scheme accurately predicts the onset of large flares and is capable of pinpointing the precise location of the flare epicenter for most events. This successful prediction suggests that the distribution of twist flux density and nonpotential field intensity within high free-energy regions (HiFER), including the polarity inversion line (PIL), is crucial in determining when, where, and how large a flare will occur. Nevertheless, the κ-scheme remains incomplete and cannot predict certain specific flares. In this presentation, we explore the reasons for the κ-scheme's limitations by analyzing the 3D magnetic field structures of various active regions using the latest nonlinear force-free magnetic field model. Furthermore, we statistically investigate the relationship between the 3D magnetic field structures of active regions and the formation of coronal mass ejections (CMEs) as well as the occurrence of solar energetic particle (SEP) events. As a result, we find that (1) the κ-scheme can be updated by considering the vertical magnetic field structure, thereby improving its predictive capability for flare occurrences, (2) the flare regions that produce CMEs can be classified more accurately by considering both the vertical distribution of the magnetic field decay rate and the ratio of direct current to return current across the PIL (Muhamad and Kusano 2025), and (3) there is a discernible relationship between the accumulated free energy of HiFER and the flares that generate SEP events. These findings suggest that analyzing the 3D magnetic field structures of active regions can provide vital information for predicting space weather events.
Kusano K, Iju T, Bamba Y, Inoue S. A physics-based method that can predict imminent large solar flares. Science. 369, 587–591 (2020).
Muhamad, J. and Kusano, K. Eruptivity of Flaring Active Regions Based on Electric Current Neutralization and Torus Instability Analysis, The Astrophysical Journal. 983, L28 (2025).
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