A Confined Partial Eruption of Double-decker Filaments

Abstract

Filament eruptions, one of the most energetic explosions on the Sun, release large quantities of magnetized plasma into the interplanetary space. Hence, the understanding of the initiation and evolution of filament eruptions can provide broader implications for space weather and geospace climate. Here, we present a confined partial eruption of double-decker structure that consisted of two vertically separated filaments on 2016 April 16. Only the upper filament erupted, and the eruption was closely associated with an episode of flux cancellation, surrounding transient brightenings, and unambiguous tether-cutting reconnections of the overlying sheared loops. However, the lower filament was nearly intact through the eruption. Interestingly, the erupting material moved along large-scale external loops and eventually arrived at remote sites, indicating a confined partial eruption. All the results show that the partial eruption involved two magnetic reconnections at least, and the bottom magnetic cancellation and internal tether-cutting reconnections between filaments both play critical roles in triggering the eruption. We conjecture that the newly formed low-lying loops due to tether-cutting reconnections and the flare loops resulting from the partial eruption likely contribute to maintaining the equilibrium of the lower filament. It is also suggested that the restriction of some large-scale external magnetic structures is crucial to turn the successful partial eruption into a confined event.