Search Publications
STiC: A multiatom non-LTE PRD inversion code for full-Stokes solar observations
Leenaarts, J.; Danilovic, S.; de la Cruz Rodríguez, J. +1 more
The inference of the underlying state of the plasma in the solar chromosphere remains extremely challenging because of the nonlocal character of the observed radiation and plasma conditions in this layer. Inversion methods allow us to derive a model atmosphere that can reproduce the observed spectra by undertaking several physical assumptions. The…
A comprehensive three-dimensional radiative magnetohydrodynamic simulation of a solar flare
Cheung, M. C. M.; De Pontieu, B.; Sainz Dalda, A. +11 more
Solar and stellar flares are the most intense emitters of X-rays and extreme ultraviolet radiation in planetary systems1,2. On the Sun, strong flares are usually found in newly emerging sunspot regions3. The emergence of these magnetic sunspot groups leads to the accumulation of magnetic energy in the corona. When the magneti…
New View of the Solar Chromosphere
De Pontieu, Bart; Carlsson, Mats; Hansteen, Viggo H.
The solar chromosphere forms a crucial, yet complex and until recently poorly understood, interface between the solar photosphere and the heliosphere. Advances in high-resolution instrumentation, adaptive optics, image reconstruction techniques, and space-based observatories allow unprecedented high-resolution views of the finely structured and hi…
Drifting of the line-tied footpoints of CME flux-ropes
Aulanier, Guillaume; Dudík, Jaroslav
Context. Bridging the gap between heliospheric and solar observations of eruptions requires the mapping of interplanetary coronal mass ejection (CME) footpoints down to the Sun's surface. But this not straightforward. Improving the understanding of the spatio-temporal evolutions of eruptive flares requires a comprehensive standard model. But the c…
Ellerman bombs and UV bursts: transient events in chromospheric current sheets
Carlsson, M.; Pereira, T. M. D.; Hansteen, V. +3 more
Context. Ellerman bombs (EBs), observed in the photospheric wings of the Hα line, and UV bursts, observed in the transition region Si IV line, are both brightenings related to flux emergence regions and specifically to magnetic flux of opposite polarity that meet in the photosphere. These two reconnection-related phenomena, nominally formed far ap…
Recovering Thermodynamics from Spectral Profiles observed by IRIS: A Machine and Deep Learning Approach
De Pontieu, Bart; Gošić, Milan; Sainz Dalda, Alberto +1 more
Inversion codes allow the reconstruction of a model atmosphere from observations. With the inclusion of optically thick lines that form in the solar chromosphere, such modeling is computationally very expensive because a non-LTE evaluation of the radiation field is required. In this study, we combine the results provided by these traditional metho…
Coronal bright points
Madjarska, Maria S.
Coronal bright points (CBPs) are a fundamental class of solar activity. They represent a set of low-corona small-scale loops with enhanced emission in the extreme-ultraviolet and X-ray spectrum that connect magnetic flux concentrations of opposite polarities. CBPs are one of the main building blocks of the solar atmosphere outside active regions u…
SI IV Resonance Line Emission during Solar Flares: Non-LTE, Nonequilibrium, Radiation Transfer Simulations
Kerr, Graham S.; Carlsson, Mats; Young, Peter R. +2 more
The Interface Region Imaging Spectrograph routinely observes the Si IV resonance lines. When analyzing quiescent observations of these lines, it has typically been assumed that they form under optically thin conditions. This is likely valid for the quiescent Sun, but this assumption has also been applied to the more extreme flaring scenario. We us…
The High-Resolution Coronal Imager, Flight 2.1
Tiwari, Sanjiv K.; Golub, Leon; Winebarger, Amy R. +49 more
The third flight of the High-Resolution Coronal Imager (Hi-C 2.1) occurred on May 29, 2018; the Sounding Rocket was launched from White Sands Missile Range in New Mexico. The instrument has been modified from its original configuration (Hi-C 1) to observe the solar corona in a passband that peaks near 172 Å, and uses a new, custom-built low-noise …
Solar Chromospheric Temperature Diagnostics: A Joint ALMA-Hα Analysis
Cranmer, Steven R.; Reardon, Kevin P.; Uitenbroek, Han +4 more
We present the first high-resolution, simultaneous observations of the solar chromosphere in the optical and millimeter wavelength ranges, obtained with the Atacama Large Millimeter Array (ALMA) and the Interferometric Bidimensional Spectrometer at the Dunn Solar Telescope. In this paper we concentrate on the comparison between the brightness temp…