Fine-scale Structures of Flux Ropes Tracked by Erupting Material

Abstract: We present the Solar Dynamics Observatory observations of two flux ropes respectively tracked out by material from a surge and a failed filament eruption on 2012 July 29 and August 04. For the first event, the interaction between the erupting surge and a loop-shaped filament in the east seems to "peel off" the filament and add bright mass into the flux rope body. The second event is associated with a C-class flare that occurs several minutes before the filament activation. The two flux ropes are respectively composed of 85$\pm$12 and 102$\pm$15 fine-scale structures, with an average width of about 1$\arcsec$.6. Our observations show that two extreme ends of the flux rope are rooted in the opposite polarity fields and each end is composed of multiple footpoints (FPs) of the fine-scale structures. The FPs of the fine-scale structures are located at network magnetic fields, with magnetic fluxes from 5.6$\times10^{18}$ Mx to 8.6$\times10^{19}$ Mx. Moreover, almost half of the FPs show converging motion of smaller magnetic structures over 10 hr before the appearance of the flux rope. By calculating the magnetic fields of the FPs, we deduce that the two flux ropes occupy at least 4.3$\times10^{20}$ Mx and 7.6$\times10^{20}$ Mx magnetic fluxes, respectively.