Ignasi Josep Soler Poquet

• Ornig, Sascha; Voort, Luc Rouppe van der; Carlsson, Mats; Baso, Carlos José Díaz; Øyre, Eilif Sommer & Poquet, Ignasi Josep Soler [Show all 7 contributors for this article] (2026). Investigating white-light flare mechanisms via the Paschen jump using high-resolution continuum observations from the Swedish 1-m Solar Telescope. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 712. doi: 10.1051/0004-6361/202660421. Full text in Research Archive Show summary

  Context. The continuum is understood to contain a large portion of the energy emitted by a solar flare. The optical continuum, known as white light (WL), is particularly relevant since it may be observed by ground-based instruments. Aims. We measured the WL enhancements short- and longward of the Paschen jump in order to gain insights into the possible mechanism(s) behind the creation of these increases in our two case studies. Methods. We took measurements from the Swedish 1-m Solar Telescope of the pseudo-continuum around the Ca II 8542 Å line as well as the true continuum around the K I 7699 Å and the Fe I 6173 Å line, providing us with observations on both sides of the Paschen jump. Results. We observe WL enhancements of over 40% against the dark (pen-) umbral background in both flares. No WL excess is detectable against the granulation outside the sunspots. The WL excess in flare 1 is co-temporal with the derivative of the GOES soft X-ray and hard X-ray (HXR) measurements from the Advanced Space-based Solar Observatory (ASO-S), and the flare is compatible with the Neupert effect. For the second flare, a preceding smaller flare may be the cause of the temporal discrepancy. Signatures of chromospheric evaporation and condensation are found in the WL area for both flares. The ratio of intensities blueward and redward of the Paschen jump (i.e., the Paschen ratio) in flare 1 is below one for most WL pixels. This is in disagreement with the accepted WL formation mechanisms, which are both of photospheric and chromospheric origin. We believe this is a consequence of the Ca II 8542 Å pseudo-continuum being affected by line wing opacity changes. Conclusions. The co-temporality of WL and HXR enhancements suggests that the WL emission enhancements in flare 1 (and parts of flare 2) are a result of direct electron precipitation. We conclude that more reliable continuum measurements free of any nearby line influence are necessary in order to obtain conclusive evidence for the formation mechanism(s) behind optical continuum enhancements from such analysis as presented in this work.

• Faber, Jonas Thoen; Joshi, Reetika; Voort, Luc Rouppe van der; Wedemeyer, Sven; Øyre, Eilif Sommer & Poquet, Ignasi J. Soler [Show all 7 contributors for this article] (2026). Fine details in solar flare ribbons: Statistical insights from observations with the Swedish 1-m Solar Telescope. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 705. doi: 10.1051/0004-6361/202556738. Full text in Research Archive Show summary

  Context. Flare ribbons serve as chromospheric footprints of energy deposition resulting from particle acceleration during magnetic reconnection. Their fine-scale structure provides a valuable tool for probing the dynamics of the flare reconnection process. Aims. Our goal is to investigate the fine-scale structure of flare ribbons through multiple observations of flares, utilising data obtained from the Atmospheric Imaging Assembly (AIA) and the Swedish 1-m Solar Telescope (SST). Methods. The aligned AIA and SST datasets for the three solar flares were used to examine their overall morphology. The SST datasets were specifically used to identify fine-scale structures within the flare ribbons. For spectroscopic analysis of these fine-scale structures, we applied machine-learning methods ( k -means clustering) and Gaussian fitting. Results. Using k -means, we identified elongated features in the flare ribbons, termed as ‘riblets’, which are short-lived and jet-like small-scale structures that extend as plasma columns from the flare ribbons. Riblets are more prominent near the solar limb and represent the ribbon front. Riblet widths are consistent across observations, ranging from 110−310 km (0.15−0.41), while vertical lengths span 620−1220 km (0.83−1.66), with a potential maximum of 2000 km (2.67), after accounting for projection effects. Detailed H β spectral analysis reveals that riblets exhibit a single, redshifted emission component, with velocities of 16−21 km s −1 , independent of the viewing angle. Conclusions. Our high-resolution observations of the three flare ribbons show that they are not continuous structures, but rather are composed of vertically extended, fine-scale substructures. These irregular features indicate that the reconnection region is not a smooth, laminar current sheet, but rather a fragmented zone filled with magnetic islands (blobs or riblets), consistent with the theory of patchy reconnection within the coronal current sheet.

• Poquet, I. J. Soler; Baso, C. J. Díaz; Voort, Luc Rouppe van der & Vissers, G. J. M. (2025). Automatic detection of Ellerman bombs using deep learning. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 699. doi: 10.1051/0004-6361/202453524. Full text in Research Archive Show summary

  Context. Ellerman bombs (EBs) are observable signatures of photospheric small-scale magnetic reconnection events. They can be seen as intensity enhancements of the H α 6563 Å line wings and as brightenings in the SDO/AIA 1600 Å and 1700 Å passbands. Reliable automatic and systematic detection of EBs would enable the study of the impact of magnetic reconnection on the Sun’s dynamics. Aims. We aim to develop a method to automatically detect EBs in H α observations from the Swedish 1-m Solar Telescope (SST) and in SDO/AIA observations using the 1600 Å, 1700 Å, 171 Å, and 304 Å passbands. Methods. We trained models based on neural networks (NNs) to perform automatic detection of EBs. Additionally, we used different types of NNs to study how different properties – such as local spatial information, the spectral shape of each pixel, or the center-to-limb variation – contribute to the detection of EBs. Results. We find that for SST observations, the NN-based models are proficient at detecting EBs. With sufficiently high spectral resolution, the spatial context is not required to detect EBs. However, as we degrade the spectral and spatial resolution, the spatial information becomes more important. Models that include both dimensions perform best. For SDO/AIA, the models struggle to reliably distinguish between EBs and bright patches of different origin. Permutation feature importance revealed that the H α line wings (around ± 1 Å from line center) are the most informative features for EB detection. For the SDO/AIA case, the 1600 Å channel is the most relevant one when used in combination with 171 Å and 304 Å. Conclusions. The combination of the four different SDO/AIA passbands is not informative enough to accurately classify EBs. From our analysis of a few sample SDO/AIA 1600 Å and 1700 Å light curves, we conclude that inclusion of the temporal variation may be a significant step towards establishing an effective EB detection method that can be applied to the extensive SDO/AIA database of observations.

View all works in NVA

• Poquet, Ignasi Josep Soler; Baso, Carlos José Díaz & Voort, Luc Rouppe van der (2026). Multi-wavelength observations of Ellerman bombs. Full text in Research Archive Show summary

  Context. Ellerman bombs (EBs) are observational signatures of small-scale magnetic reconnection, key to understanding the lower solar atmosphere. While their role in active regions has been widely studied using the Hα line, near-ultraviolet (NUV) spectra routinely observed by the Interface Region Imaging Spectrograph (IRIS) offer a promising alternative for EB identification, enabling large-scale studies. Aims. We aim to identify the most important spectral signatures of EBs in the IRIS NUV spectra. With this, we seek to develop a robust criterion for their detection solely using the IRIS NUV spectra. In parallel, we determine the typical atmospheric stratification associated with EBs. Methods. We used four coordinated observations between the Swedish 1-m Solar Telescope (SST) and IRIS. Using the Hα line as a reference, we detected 18 different EBs and studied their associated IRIS NUV spectra. In addition, we used the IRIS2+ inversion tool to infer the temperature, line-of-sight velocity, and non-thermal broadening from the EB spectra. Results. The defining feature of EBs in the IRIS NUV is the enhancement of the wings of the subordinated Mg ii triplet between the Mg ii h&k lines. Inversions reveal that these signatures are produced by a localized temperature increase of ∆T ∼ 1670 K around log(τ)= −3.8. Using only the Mg ii triplet signatures, we found a detection criterion that successfully recovered 14 of 18 Hα-detected EBs. In addition, the shape of the Mg ii h&k lines in relation to the Mg ii triplet can serve as a proxy for the EB formation height. Conclusions. The NUV spectrum observed by IRIS is a good candidate for detecting EBs, opening the doors to large-scale studies across the extensive IRIS database, removing the dependence on Hα observations. This capability bridges the gap between small- and large-scale event studies, which was not possible before due to the lack of coordinated observations.

• Poquet, Ignasi Josep Soler; Baso, Carlos José Díaz & Voort, Luc Rouppe van der (2025). Ellerman bombs detection in SST and SDO using Deep Learning. Full text in Research Archive
• Poquet, Ignasi Josep Soler; Baso, Carlos José Díaz & Voort, Luc Rouppe van der (2024). Detecting Ellerman bombs with Deep Learning. Full text in Research Archive
• Poquet, Ignasi Josep Soler (2024). Ellerman bombs detection in SST and SDO observations with Deep Learning. Full text in Research Archive
• Poquet, Ignasi Josep Soler; Voort, Luc H.M. Rouppe van der & Baso, Carlos José Díaz (2023). Interpretación de observaciones solares usando redes neuronales. Full text in Research Archive
• Poquet, Ignasi Josep Soler; Voort, Luc H.M. Rouppe van der & Baso, Carlos José Díaz (2023). Interpretation of Solar Observations with Deep Learning. Full text in Research Archive
• Mardal, Kent-Andre; Evju, Øyvind; Soler, Jose & Frangi, Alex (2016). Robustness of common hemodynamics indicators with respect to numerical resolution in 38 middle cerebral artery aneurysms. Full text in Research Archive

View all works in NVA