From fundamental theory to realistic modeling of the birth of solar eruptions

Solar eruptions,primarily manifested as solar flares,filament eruptions and coronal mass ejections,represent explosive releases of magnetic energy stored in the solar corona,with the potential to drive severe space weather.The initiation of solar eruptions remains an open question,leading to various theoretical models that are inferred from observations.However,these models are subjects of debate due to the absence of direct measurements of the three-dimensional(3D)magnetic fields in the corona.Numerical simulations,based on solving magnetohydrodynamics(MHD)equations that govern the macroscopic dynamics of solar corona,serve as a touchstone for testing these theoretical models.One early proposed model suggested that eruptions could be triggered by reconnection within a single sheared magnetic arcade,which is known as the tether-cutting reconnection model,but it was never confirmed through 3D MHD simulations until very recently.Consequently,two models have gained more popularity:one involving the eruption of a twisted magnetic flux rope(MFR)due to ideal instability(or loss of equilibrium),and the other known as the breakout eruption,which requires a quadrupolar configuration with a delicately located magnetic null point.Other mixed mechanisms,involving both ideal instability and reconnection,are also proposed in association with localized magnetic flux emergence.Now with the validation of the tether-cutting model,the fundamental mechanisms are boiled down to two types of models,one primarily based on the ideal instability of a pre-existing MFR,and the other based on the reconnection of sheared field lines with or without an MFR.Recently,the modelling of the birth of solar eruption using observed data-based MHD simulations has advanced rapidly,becoming a crucial research tool in the study of the initiation mechanisms.These realistic modellings reveal a higher level of complexity compared to all currently available theories and idealized models.