Solar magnetic flux rope eruptions caused by inverse flux feeding processes

TL;DR

This study uses 2.5D MHD simulations to demonstrate that inverse flux feeding can trigger solar eruptions by increasing the unsigned axial magnetic flux, similar to normal flux feeding, highlighting the importance of unsigned flux in eruption onset.

Contribution

It reveals that inverse flux feeding, where flux directions oppose, can also cause eruptions by increasing unsigned flux, expanding understanding of eruption mechanisms.

Findings

Inverse flux feeding causes eruptions by increasing unsigned flux.

Eruption thresholds are similar for normal and inverse flux feeding.

Unsigned axial magnetic flux regulates eruption onset.

Abstract

Large-scale solar eruptions are generally accepted to have coronal magnetic flux ropes as their core structures. Recent studies found that the solar eruptions could be initiated by a sequence of flux feeding processes, during with chromospheric fibrils rise and merge with the pre-existing coronal flux rope. Further theoretical analyses have demonstrated that the normal flux feeding, i.e. 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, so as to initiate the eruption. If the directions of the axial flux in the fibril and the flux rope are opposite, it is termed inverse flux feeding, whose influence on coronal flux ropes, however, is still unclear. In this paper, we use a 2.5-dimensional magnetohydrodynamic model to simulate the evolution of coronal flux ropes associated with inverse flux feeding. It is 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 if 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 caused by both normal and inverse flux feeding. Our simulation results suggest that it is the unsigned axial magnetic flux rather than the signed axial flux that regulates the onset of coronal flux rope eruptions.