Aline Rangøy Brunvoll

• 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.

• Wilde, M. De; Pietrow, A. G. M.; Druett, M. K.; Yabar, A. Pastor; Koza, J. & Kontogiannis, I. [Show all 25 contributors for this article] (2025). Synthesizing Sun-as-a-star flare spectra from high-resolution solar observations. Astronomy and Astrophysics (A & A). ISSN 0004-6361. 700. doi: 10.1051/0004-6361/202554870. Full text in Research Archive Show summary

  Context. Spatially resolved observations of the Sun and the astronomical sample size of stellar bodies are the respective key strengths of solar and stellar observations. However, the large difference in object brightness between the Sun and other stars has led to distinctly different instrumentation and methodologies between the two fields. Aims. We produced and analyzed synthetic full-disk spectra derived from 19 small area field-of-view optical observations of solar flares acquired by the Swedish 1-m Solar Telescope (SST) between 2011 and 2024. These were used to investigate what can and cannot be inferred about physical processes on the Sun from Sun-as-a-star observations. Methods. The recently released Numerical Empirical Sun-as-a-Star Integrator (NESSI) code provides synthetic full-disk integrated spectral line emission based on smaller field-of-view input while accounting for center-to-limb variations and differential rotation. We used this code to generate pseudo-Sun-as-a-star spectra from the SST observations. Results. We show that limited-area solar observations can be extrapolated to represent the full disk accurately in a manner close to what is achievable with Sun-as-a-star telescopes. Additionally, we identify nine spectral features, four of which are caused by instrumental effects. Most notably, we find a relation between the heliocentric angle of flares and the width of the excess emission left by them as well as a source of false positive coronal mass ejections-like signatures, and we defined an energy scaling law based on chromospheric line intensities that shows that the peak flare contrast roughly scales with the square root of the bolometric energy. Conclusions. The presented method of creating pseudo-Sun-as-a-star observations from limited field-of-view solar observations allows for the accurate comparison of solar flare spectra with their stellar counterparts while allowing for the detection of signals at otherwise unachievable noise levels.

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• Kirkaune, Mats; Wedemeyer, Sven; Carlsson, Mats & Brunvoll, Aline Rangøy (2026). Exploring synthetic nanoflare signatures at millimetre wavelengths. Full text in Research Archive Show summary

  Nanoflares have long been considered to be promising candidates for heating the solar corona to millions of degrees. However, their assumed small sizes, short durations, and subtle signals in accessible observables have made direct detection difficult. In the millimetre regime, the Atacama Large (sub-)Millimeter Array (ALMA) offers the capability of measuring chromospheric temperatures at very high temporal and comparatively high spatial resolution. Yet, it is not clear if the currently offered solar observing mode of ALMA is capable of detecting nanoflares. To explore possible millimetre signatures of nanoflares, the F-CHROMA grid of 1D RADYN flare models has been extended to lower total flare energies, into the nanoflare domain. These models simulate the response of a coronal loop to an electron beam inserted at its top. The new simulations were run as a combined effort to characterise nanoflare signatures at different wavelengths. The radiative transfer code RH1.5 was used to compute the millimetre signatures of the modelled nanoflares. These signatures were then degraded to the temporal and spatial resolution achievable with ALMA. The synthetic ALMA light curves indicate that, in principle, ALMA should be able to detect nanoflare signatures, especially when using wider array configurations in combination with a higher frequency band to maximise spatial resolution. This suggests that dedicated ALMA observations could, in principle, place important constraints on atmospheric heating from nanoflares.

• Aakre, Gina & Brunvoll, Aline Rangøy (2026). I kveld kan vi se månen dekke nesten hele sola. [Internet]. Forskning.no. Full text in Research Archive Show summary

  Mens vi ser på formørkelsen, prøver solforsker Aline Rangøy Brunvoll å nøste i et av solas største mysterier. Hvorfor er den ytterste atmosfæren varmere enn overflaten?

• Aakre, Gina & Brunvoll, Aline Rangøy (2026). I kveld kan vi se månen dekke nesten hele sola - Titan.uio.no. Full text in Research Archive
• Brunvoll, Aline Rangøy (2026). Arbeidsliv, Nyheter | Aline (26) tar doktorgrad i solforskning. Full text in Research Archive Show summary

  26 år gamle Aline Rangøy Brunvoll fra Jeløy er såpass fascinert av sola at hun nå er midt i en doktorgrad innen solforskning.

• Åkervall, Bente Storsveen & Brunvoll, Aline Rangøy (2026). Mossejenta Aline gjør doktorgrad i solfysikk på La Palma. Full text in Research Archive Show summary

  26 år gamle Aline Rangøy Brunvoll fra Moss forsker på solen ved Roque de los Muchachos-observatoriet på La Palma. Møt den norske doktorgradsstudenten som studerer nanoflares og solens mysterier.

• Brønn, Kathrine; Stenbek, Finn Børge & Brunvoll, Aline Rangøy (2026). Eftan: Et aldri så lite sol-mysterium - Distriktsprogram - Østfold - NRK Radio. [Radio]. NRK. Full text in Research Archive Show summary

  Goood mandag! Finn Børge og Kathrine er stemmene i radioen din denne uka. Vi forsker litt på sola, sammen med mossingen Aline. Hun tar doktorgard i solfysikk ved UiO.

• Brønn, Kathrine; Stenbek, Finn Børge & Brunvoll, Aline Rangøy (2026). Mossing forsker på sola: Bruker digert teleskop – NRK. [Internet]. NRK. Full text in Research Archive Show summary

  Aline Rangøy Brunvoll elsker sola - ikke for å bli brun, men for å lære mer om alle mysterier på - og rundt den. Da bruker hun et digert teleskop som står på kanariøya La Palma.

• Grøndahl, Beate & Brunvoll, Aline Rangøy (2026). Morran: Vi teller geitekillinger! - Distriktsprogram - Østfold - NRK Radio. [Radio]. NRK. Full text in Research Archive Show summary

  God morgen Østfold! Beate og Kathrine våkner opp med deg på en dag hvor vi drømmer oss til La Palma hvor mossingen Aline forsker på sola. Møt henne i Morran i Østfold

• Kirkaune, Mats; Brunvoll, Aline Rangøy & Saberi, Maryam (2024). Avsløring av solas hemmeligheter. Full text in Research Archive

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