Gradual Magnetic Evolution of Sunspot Structure and Filament-Corona Dynamics Associated with the X1.8 Flare in AR 11283

TL;DR

This study investigates the gradual magnetic and structural changes in sunspots and filaments leading up to a major solar flare, revealing long-term pre-flare evolution and potential triggering mechanisms.

Contribution

It provides new insights into the long-term pre-flare magnetic evolution and the role of filament rise and reconnection in triggering large solar eruptions.

Findings

Gradual penumbral decay observed before the flare

Coronal arcade expansion correlates with filament rise

Reconnection processes may trigger major eruptions

Abstract

In this paper, we present a study on persistent and gradual penumbral decay and correlated decline of the photospheric transverse field component during 10-20 hours before a major flare (X1.8) eruption on 2011 September 7. This long-term pre-eruption behavior is corroborated with the well-imaged pre-flare filament rising, the consistent expansion of coronal arcades overlying the filament, as well as the NLFFF modelling results in the literature. We suggest that both the long-term pre-flare penumbral decay and the transverse field decline are the photospheric manifestation of the gradual rise of the coronal filament-flux rope system. We also suggest that a C3 flare and subsequent reconnection process preceding the X1.8 flare play an important role in triggering the later major eruption.