Solar magnetic flux rope eruptions caused by inverse flux feeding processes

¹ School of Earth and Space Sciences, University of Science and Technology of China, Hefei 230026, China
² CAS Center for Excellence in Comparative Planetology/CAS Key Laboratory of Geospace Environment/Mengcheng National Geophysical Observatory, University of Science and Technology of China, Hefei 230026, China
³ Collaborative Innovation Center of Astronautical Science and Technology, Hefei 230026, China
⁴ Key Laboratory of Solar Activity, National Astronomical Observatories, Chinese Academy of Sciences, 100012 Beijing, China
⁵ University of Chinese Academy of Sciences, 100049 Beijing, China
⁶ Anhui Jianzhu University, Hefei 230026, China
⁷ College of Physics and Electric Information, Luoyang Normal University, Luoyang, Henan 471934, China
⁸ National Key Laboratory of Deep Space Exploration, University of Science and Technology of China, Hefei 230026, China
⁹ Hefei National Laboratory, University of Science and Technology of China, Hefei 230088, China

^⋆ Corresponding author: zhangqh@ustc.edu.cn

Received: 16 May 2025
Accepted: 4 August 2025

Abstract

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.