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The bulk of the radiative output of a solar flare is emitted from the chromosphere, which produces enhancements in the optical and UV continuum, and in many lines, both optically thick and thin. We have, until very recently, lacked…

Solar and Stellar Astrophysics · Physics 2015-10-07 Graham S. Kerr , Paulo J. A. Simões , Jiong Qiu , Lyndsay Fletcher

A three-dimensional picture of the solar atmosphere's thermodynamics can be obtained by jointly analyzing multiple spectral lines that span many formation heights. In paper I, we found strong correlations between spectral shapes from a…

Solar and Stellar Astrophysics · Physics 2021-07-21 Brandon Panos , Lucia Kleint

Mg II lines represent one of the strongest emissions from the chromospheric plasma during solar flares. In this article, we studied the Mg II lines observed during the X1 flare on March 29 2014 (SOL2014-03-29T17:48) by IRIS. IRIS detected…

Solar and Stellar Astrophysics · Physics 2015-12-09 W. Liu , P. Heinzel , L. Kleint , J. Kasparova

In this work we leverage a weakly-labeled dataset of spectral data from NASAs IRIS satellite for the prediction of solar flares using the Multiple Instance Learning (MIL) paradigm. While standard supervised learning models expect a label…

Solar and Stellar Astrophysics · Physics 2022-11-21 Cédric Huwyler , Martin Melchior

The flare activity of the Sun has been studied for decades, using both space- and ground-based telescopes. In particular, the Interface Region Imaging Spectrograph (IRIS) provides unique diagnostics to investigate the thermodynamics of…

Solar and Stellar Astrophysics · Physics 2022-11-11 Alberto Sainz Dalda , Bart De Pontieu

The prediction of solar flares is of practical and scientific interest; however, many machine learning methods used for this prediction task do not provide the physical explanations behind a model's performance. We made use of two recently…

Solar and Stellar Astrophysics · Physics 2023-03-08 Brandon Panos , Lucia Kleint , Jonas Zbinden

The Mg II h&k doublet are two of the primary spectral lines observed by the Sun-pointing Interface Region Imaging Spectrograph (IRIS). These lines are tracers of the magnetic and thermal environment that spans from the photosphere to the…

Solar and Stellar Astrophysics · Physics 2015-10-07 Donald Schmit , Paul Bryans , Bart De Pontieu , Scott McIntosh , Jorrit Leenaarts , Mats Carlsson

NASA's Interface Region Imaging Spectrograph (IRIS) small explorer mission will study how the solar atmosphere is energized. IRIS contains an imaging spectrograph that covers the Mg II h&k lines as well as a slit-jaw imager centered at Mg…

Solar and Stellar Astrophysics · Physics 2015-06-16 J. Leenaarts , T. M. D. Pereira , M. Carlsson , H. Uitenbroek , B. de Pontieu

With machine learning entering into the awareness of the heliophysics community, solar flare prediction has become a topic of increased interest. Although machine learning models have advanced with each successive publication, the input…

Solar and Stellar Astrophysics · Physics 2020-03-11 Brandon Panos , Lucia Kleint

The Interface Region Imaging Spectrograph (IRIS) has routinely observed the flaring Mg II NUV spectrum, offering excellent diagnostic potential and a window into the location of energy deposition. A number of studies have forward modelled…

Solar and Stellar Astrophysics · Physics 2019-10-02 G. S. Kerr , Joel C. Allred , Mats Carlsson

The Mg ii h&k lines are key diagnostics of the solar chromosphere. They are sensitive to the temperature, density, and non-thermal velocities in the chromosphere. The average Mg ii h&k line profiles arising from previous 3D chromospheric…

Solar and Stellar Astrophysics · Physics 2024-11-27 P. Ondratschek , D. Przybylski , H. N. Smitha , R. Cameron , S. K. Solanki , J. Leenaarts

Solar flares show highly unusual spectra, in which the thermodynamic conditions of the solar atmosphere are encoded. Current models are unable to fully reproduce the spectroscopic flare observations, especially the single-peaked spectral…

Solar and Stellar Astrophysics · Physics 2017-06-28 Fatima Rubio da Costa , Lucia Kleint

The Mg II h&k lines are amongst the best diagnostic tools of the upper solar chromosphere. This region of the atmosphere is of particular interest as it is the lowest region of the Sun's atmosphere where the magnetic field is dominant in…

Solar and Stellar Astrophysics · Physics 2023-03-01 Viggo Hansteen , Juan Martinez Sykora , Mats Carlsson , Bart De Pontieu , Milan Gosic , Souvik Bose

The IRIS Mg II k line serves as a very good tool to diagnose the heating processes in solar flares. Recent studies have shown that apart from the usual red asymmetries which are interpreted as the result of condensation downflows, this line…

Solar and Stellar Astrophysics · Physics 2020-04-23 Jie Hong , Ying Li , M. D. Ding , Yu-Hao Zhou

Spectral lines allow us to probe the thermodynamics of the solar atmosphere, but the shape of a single spectral line may be similar for different thermodynamic solutions. Multiline analyses are therefore crucial, but computationally…

Solar and Stellar Astrophysics · Physics 2021-05-19 Brandon Panos , Lucia Kleint , Sviatoslav Voloshynovskiy

We use radiation hydrodynamic simulations to examine two models of solar flare chromospheric heating: Alfv\'en wave dissipation and electron beam collisional losses. Both mechanisms are capable of strong chromospheric heating, and we show…

Solar and Stellar Astrophysics · Physics 2016-08-17 Graham S. Kerr , Lyndsay Fletcher , Alexander J. B. Russell , Joel C. Allred

The bulk of solar flare energy is deposited in the chromosphere. Flare ribbons and footpoints in the chromosphere therefore offer great diagnostic potential of flare energy release and transport processes. High quality observations from the…

Solar and Stellar Astrophysics · Physics 2023-10-12 Graham S. Kerr , Adam F. Kowalski , Joel C. Allred , Adrian N. Daw , Melissa R. Kane

Spectroscopic observations of solar flares provide critical diagnostics of the physical conditions in the flaring atmosphere. Some key features in observed spectra have not yet been accounted for in existing flare models. Here we report a…

Solar and Stellar Astrophysics · Physics 2016-08-16 Fatima Rubio da Costa , Lucia Kleint , Vahé Petrosian , Wei Liu , Joel C. Allred

Inversion codes allow reconstructing a model atmosphere from observations. With the inclusion of optically thick lines that form in the solar chromosphere, such modelling is computationally very expensive because a non-LTE evaluation of the…

Solar and Stellar Astrophysics · Physics 2019-04-19 Alberto Sainz Dalda , Jaime de la Cruz Rodríguez , Bart De Pontieu , Milan Gošić

We analyze observations from the Interface Region Imaging Spectrograph of the Mg II k line, the Mg II UV subordinate lines, and the O I 135.6 nm line to better understand the solar plage chromosphere. We also make comparisons with…

Solar and Stellar Astrophysics · Physics 2015-08-21 Mats Carlsson , Jorrit Leenaarts , Bart De Pontieu
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