A Chain of Evolutionary Processes Forming the Core Structure(s) Responsible for Solar Eruptions

^{We describe a sequence of evolutionary processes leading to eruptive instabilities in solar active regions. The sequence initiates from cases of magnetic flux emergence giving rise to strong magnetic polarity inversion lines (PILs) in active regions. Here, a strong PIL refers to local photospheric magnetic field strength exceeding the equipartition value, thus giving rise to velocity and magnetic shear due to Lorentz tension along the PIL. This manifests initially as a shear magnetic arcade (SMA). Due to magnetic flux cancellation or magnetic reconnection, in general, along these PILs, as well as the overarching magnetic helicity conservation principle, the sheer mutual helicity of SMAs is gradually transformed into self helicity (twist and writhe), giving rise to the gradual formation of a magnetic flux rope (MFR) in the corona above the PIL. The MFR distinguishes itself from the overlaying large-scale coronal fields and enters into a sequence of metastable states fueled by continuous flux emergence along the PIL and the continuing, confined magnetic reconnection episodes. The MFR finally reaches a state of marginal stability that is prone to an eruptive instability given its total twist, the situation in the overlaying corona (i.e., possible null point(s)), the orientation of the overlaying, strapping fields and their decay with height. At least one eruption will occur at some point due to any one of the above reasons. In conclusion, we describe a sequence of events that point to a SMA - MFR transition if the initial SMA is let to evolve for sufficient time. Avenues to provide evidence for this interpretation of solar eruptions are also highlighted and discussed.}

^{Partial support for this work has been provided by the Astroinformatics Cluster of the Department of Physics and Astronomy at Georgia State University.}