Gradual magnetic evolution of sunspot structure and filament-corona dynamics associated with the x1.8 flare in ar11283

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