The formation of an inverse S-shaped active-region filament driven by sunspot motion and magnetic reconnection

TL;DR

This study investigates the formation and eruption of an inverse S-shaped solar filament driven by sunspot motion and magnetic reconnection, combining observations and magnetic field extrapolation.

Contribution

It provides detailed observational evidence of filament formation via sunspot rotation and magnetic cancellation, and explores the filament's magnetic structure.

Findings

Sunspot rotation contributed to filament formation.

Magnetic cancellation was associated with filament brightening.

The filament likely had a twisted magnetic structure.

Abstract

We present a detailed study of the formation of an inverse S-shaped filament prior to its eruption in active region NOAA 11884 from October 31 to November 2, 2013. In the initial stage, clockwise rotation of a small positive sunspot around the main negative trailing sunspot formed a curved filament. Then the small sunspot cancelled with negative magnetic flux to create a longer active-region filament with an inverse S-shape. At the cancellation site a brightening was observed in UV and EUV images and bright material was transferred to the filament. Later the filament erupted after cancellation of two opposite polarities under the upper part of the filament. Nonlinear force-free field (NLFFF) extrapolation of vector photospheric fields suggests that the filament may have a twisted structure, but this cannot be confirmed from the current observations.