Solar magnetic flux rope eruptions caused by inverse flux feeding processes

The core structures of large-scale solar eruptions are generally accepted to be coronal magnetic flux ropes. Recent studies found that solar eruptions can be initiated by a sequence of flux feeding processes during with chromospheric fibrils rise and merge with the preexisting coronal flux rope. Further theoretical analyses demonstrated that the normal flux feeding, that is, the axial magnetic flux within the fibril is in the same direction as that in the flux rope, results in the accumulation of the total axial flux within the flux rope, which initiates the eruption. When the directions of the axial flux in the fibril and the flux rope are opposite, it is called inverse flux feeding. The effect of inverse flux feeding on coronal flux ropes, however, is still unclear. In this paper, we used a 2.5-dimensional magnetohydrodynamic model to simulate the evolution of coronal flux ropes associated with inverse flux feeding. We found that inverse flux feeding is also efficient in causing solar eruptions: Although the total signed axial magnetic flux of the rope decreases after inverse flux feeding, the total unsigned axial flux can accumulate; the eruption occurs when the unsigned axial flux of the rope reaches a critical value, which is almost the same as the threshold for normal flux feeding. The total axial currents within the rope are also similar during the onset of the eruptions that are caused by both normal and inverse flux feeding. Our simulation results suggest that the unsigned axial magnetic flux rather than the signed axial flux regulates the onset of coronal flux rope eruptions.