Buildup of the Magnetic Flux Ropes in Homologous Solar Eruptions

TL;DR

This study investigates how magnetic flux ropes (MFRs) form and evolve along a collisional polarity inversion line (cPIL) in homologous solar eruptions, highlighting the role of magnetic cancellation and shearing in energy buildup.

Contribution

It provides new insights into the formation of MFRs through magnetic cancellation and shearing along cPILs during homologous eruptions, using a flux deficit method and detailed magnetic analysis.

Findings

Magnetic cancellation along cPIL is about 24% of total flux.

Magnetic fields near cPIL are highly sheared with angles above 70°.

MFRs exhibit rapid twist expansion driven by collisional shearing.

Abstract

Homologous coronal mass ejections (CMEs) are an interesting phenomenon, and it is possible to investigate the formation of CMEs by comparing multi-CMEs under a homologous physical condition. AR 11283 had been present on the solar surface for several days when a bipole emerged on 2011 September 4. Its positive polarity collided with the pre-existing negative polarity belonging to a different bipole, producing recurrent solar activities along the polarity inversion line (PIL) between the colliding polarities, namely the so-called collisional PIL (cPIL). Our results show that a large amount of energy and helicity were built up in the form of magnetic flux ropes (MFRs), with recurrent release and accumulation processes. These MFRs were built up along the cPIL. A flux deficit method is adopted and shows that magnetic cancellation happens along the cPIL due to the collisional shearing scenario proposed by Chintzoglou et al. The total amount of canceled flux was $\sim$0.7$\times$10$^{21}$ Mx with an uncertainty of $\sim$13.2$\%$ within the confidence region of the 30$^\circ$ sun-center distance. The canceled flux amounts to 24$\%$ of the total unsigned flux of the bipolar magnetic region. The results show that the magnetic fields beside the cPIL are very sheared, and the average shear angle is above 70$^\circ$ after the collision. The fast expansion of the twist kernels of the MFRs and the continuous eruptive activities are both driven by the collisional shearing process. These results are important for better understanding the buildup process of the MFRs associated with homologous solar eruptions.