| Presentation Title: | Is the Mg II triplet emission a distinct flare precursor? |
| Author(s): | Jonas A. Zbinden, Lucia Kleint |
Abstract:
The trigger mechanism of solar flares is still unclear, and whether a trigger may exist in chromospheric layers. Brightenings, enhanced X-ray emission, and particular spectral properties, such as Mg II triplet emission were found before flare onset. Studies on flare precursors based on Mg II spectra were based on labeling full IRIS observations as either flaring or not, which has the drawback that no clear distinction between solar features within an observation is done. We aim to identify flare precursors in spectra, and in particular investigate the role of the chromospheric Mg II triplet as a flare precursor, because it was found in several studies as particularly distinctive. We use different machine learning methods, such as VAEs and CNNs, to establish a new spectra-based labeling scheme and train CNNs on the newly labeled data in Mg II h&k spectral line at identifying flare precursors. With a new triplet finding algorithm we track the appearance and strength of triplet emission before flares. We show a quantitative comparison of where the triplet emission appears before a flare and where it appears in non-flaring regions. Additionally, we compare the strength of the triplet emission with increases in intensity in the near-UV and far-UV. We find that the triplet emission is a distinct flare precursor in the IRIS spectral range and we speculate that this is because of chromospheric heating before flares.