Eruptions from coronal bright points: A spectroscopic view by IRIS of a mini-filament eruption, QSL reconnection, and reconnection-driven outflows

TL;DR

This study uses IRIS spectroscopic and imaging data to analyze a mini-filament eruption from a coronal bright point, revealing reconnection-driven outflows, QSL reconnection, and micro-flare dynamics in the solar atmosphere.

Contribution

It provides a detailed spectroscopic and imaging analysis of a mini-filament eruption linked to QSL reconnection, highlighting the role of small-scale magnetic flux cancellation.

Findings

Detection of reconnection outflows along elongated bright features.

Identification of QSL reconnection site with explosive event spectral signatures.

Observation of sigmoid-shaped evolution of erupting filament edges.

Abstract

The present study investigates a mini-filament eruption associated with cancelling magnetic fluxes. The eruption originates from a small-scale loop complex commonly known as a Coronal Bright Point (CBP). The event is uniquely recorded in both the imaging and spectroscopic data taken with IRIS. We analyse IRIS spectroscopic and slit-jaw imaging observations as well as images taken in the extreme-ultraviolet channels of AIA, and line-of-sight magnetic-field data from HMI onboard the SDO. We also employ an NLFFF relaxation approach based on the HMI magnetogram time series. We identify a strong small-scale brightening as a micro-flare in a CBP. The mini-eruption manifests with the ejection of hot (CBP loops) and cool (mini-filament) plasma recorded in both the imaging and spectroscopic data. The micro-flare is preceded by the appearance of an elongated bright feature in the IRIS slit-jaw 1400 A images located above the polarity inversion line. The micro-flare starts with an IRIS pixel size brightening and propagates bi-directionally along the elongated feature. We detect in both the spectral and imaging IRIS data and AIA data, strong flows along and at the edges of the elongated feature which we believe represent reconnection outflows. Both edges of the elongated feature that wrap around the edges of the erupting MF evolve into a J-type shape creating a sigmoid appearance. A quasi-separatrix layer (QSL) is identified in the vicinity of the polarity inversion line by computing the squashing factor Q in different horizontal planes of the NLFFF model. The QSL reconnection site has the same spectral appearance as the so-called explosive events identified by strong blue- and red-shifted emission, thus answering a long outstanding question about the true nature of this spectral phenomenon.