Morphology of Twisted Flux Ropes and Plasma Motions in a Prominence‐Cavity System Observed From Two Opposite Viewpoints

Abstract We investigate the three‐dimensional structures of a prominence‐cavity system from two distinct vantage points. For this purpose, we have used the observations recorded by the Atmospheric Imaging Assembly on board the Solar Dynamics Observatory and the Extreme Ultraviolet Imager (EUVI) on board the Solar Terrestrial Relations Observatory ‐ Ahead (STEREO‐A). Our analysis reveals that the prominence‐cavity system was formed by the emergence of two oppositely rotating magnetic structures from the photosphere. The cavity, identified as an intensity‐depleted region located above the prominence, was surrounded by horn‐like structures. These prominence‐horns, observed by both observatories, unveiled the presence of twisted flux ropes within the cavity. As the system evolved, we observed the prominence horns undergoing repeated upward motion accompanied by multiple instances of downward plasma motions. These observations suggest the occurrence of magnetic reconnection processes within the prominence‐cavity system. We tracked the dynamics of these plasma motions in details, estimating their average speeds, physical parameters including the temperature, magnetic field, and the plasma density. In its final stage, the structure exhibited positive helicity, with left‐bearing barbs that reflected the twisted flux rope morphology of the prominence. Our findings indicate that the prominence‐cavity system was non‐eruptive due to the presence of oppositely directed twist and writhe, which helped to conserve it's helicity.