Supergranular-scale magnetic flux emergence beneath an unstable filament

TL;DR

This study presents multi-wavelength observations of a supergranular-scale magnetic flux emergence beneath a large solar filament, linking it to the filament's eruption and subsequent coronal mass ejection, with implications for solar eruption prediction.

Contribution

It provides new evidence of how small-scale magnetic flux emergence can trigger filament eruptions and CMEs, enhancing understanding of solar magnetic activity.

Findings

Magnetic flux emergence occurred near a large filament in the photosphere.

Reconnection beneath the filament was observed, likely triggering the eruption.

The eruption was smooth and possibly driven by torus instability aided by flux emergence.

Abstract

Here we report evidence of a large solar filament eruption on 2013, September 29. This smooth eruption, which passed without any previous flare, formed after a two-ribbon flare and a coronal mass ejection towards Earth. The coronal mass ejection generated a moderate geomagnetic storm on 2013, October 2 with very serious localized effects. The whole event passed unnoticed to flare-warning systems. We have conducted multi-wavelength analyses of the Solar Dynamics Observatory through Atmospheric Imaging Assembly (AIA) and Helioseismic and Magnetic Imager (HMI) data. The AIA data on 304, 193, 211, and 94 \AA sample the transition region and the corona, respectively, while HMI provides photospheric magnetograms, continuum, and linear polarization data, in addition to the fully inverted data provided by HMI. [...] We have observed a supergranular-sized emergence close to a large filament in the boundary of the active region NOAA11850. Filament dynamics and magnetogram results suggest that the magnetic flux emergence takes place in the photospheric level below the filament. Reconnection occurs underneath the filament between the dipped lines that support the filament and the supergranular emergence. The very smooth ascent is probably caused by this emergence and torus instability may play a fundamental role, which is helped by the emergence.