Observing the release of twist by magnetic reconnection in a solar filament eruption.

Zhike Xue,Li Zhao,Kai Yang,Jun Zhang,Yingna Su,Xiaoli Yan,Xin Cheng,Liheng Yang,Yi Bi,Yongyuan Xiang,Zhong Liu,Bernhard Kliem

doi:10.1038/ncomms11837

Abstract

Magnetic reconnection is a fundamental process of topology change and energy release, taking place in plasmas on the Sun, in space, in astrophysical objects and in the laboratory. However, observational evidence has been relatively rare and typically only partial. Here we present evidence of fast reconnection in a solar filament eruption using high-resolution H-alpha images from the New Vacuum Solar Telescope, supplemented by extreme ultraviolet observations. The reconnection is seen to occur between a set of ambient chromospheric fibrils and the filament itself. This allows for the relaxation of magnetic tension in the filament by an untwisting motion, demonstrating a flux rope structure. The topology change and untwisting are also found through nonlinear force-free field modelling of the active region in combination with magnetohydrodynamic simulation. These results demonstrate a new role for reconnection in solar eruptions: the release of magnetic twist.

Highlights

Magnetic reconnection is a fundamental process of topology change and energy release, taking place in plasmas on the Sun, in space, in astrophysical objects and in the laboratory
The dynamics of this source region model are studied in a data-constrained magnetohydrodynamic (MHD) simulation, which reproduces the observed features of the eruption and confirms that the untwisting of the erupted flux is enabled by reconnection with ambient current-free flux
To further substantiate the occurrence of reconnection triggered by the erupting filament, we model the event in an MHD simulation whose initial and boundary conditions are constrained by the Helioseismic and Magnetic Imager (HMI) data

Summary

Introduction

Magnetic reconnection is a fundamental process of topology change and energy release, taking place in plasmas on the Sun, in space, in astrophysical objects and in the laboratory. The topology change and untwisting are found through nonlinear force-free field modelling of the active region in combination with magnetohydrodynamic simulation These results demonstrate a new role for reconnection in solar eruptions: the release of magnetic twist. Photospheric vector magnetograms taken by the Helioseismic and Magnetic Imager (HMI)[34] on board SDO allow us to obtain the 3D field structure of the reconnection region, independently demonstrating the change of topology. The dynamics of this source region model are studied in a data-constrained magnetohydrodynamic (MHD) simulation, which reproduces the observed features of the eruption and confirms that the untwisting of the erupted flux is enabled by reconnection with ambient current-free flux

Methods

Results

Conclusion