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…
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…
A method for global inversion of multi-resolution solar data
de la Cruz Rodríguez, J.
Understanding the complex dynamics and structure of the upper solar atmosphere strongly benefits from the use of a combination of several diagnostics. Frequently, such diverse diagnostics can only be obtained from telescopes and/or instrumentation operating at widely different spatial resolution. To optimize the utilization of such data, we propos…
Plasmoid-mediated reconnection in solar UV bursts
Peter, H.; Chitta, L. P.; Young, P. R. +1 more
Context. Ultraviolet bursts are transients in the solar atmosphere with an increased impulsive emission in the extreme UV lasting for one to several tens of minutes. They often show spectral profiles indicative of a bi-directional outflow in response to magnetic reconnection.
Aims: To understand UV bursts, we study how motions of magnetic ele…
Characterization and formation of on-disk spicules in the Ca II K and Mg II k spectral lines
Joshi, Jayant; Rouppe van der Voort, Luc; Henriques, Vasco M. J. +1 more
We characterize, for the first time, type-II spicules in Ca II K 3934 Å using the CHROMIS instrument at the Swedish 1 m Solar Telescope. We find that their line formation is dominated by opacity shifts with the K3 minimum best representing the velocity of the spicules. The K2 features are either suppressed by the Doppler-shif…
Three-dimensional modeling of chromospheric spectral lines in a simulated active region
Cheung, Mark C. M.; Rempel, Matthias; Danilovic, Sanja +4 more
Context. Because of the complex physics that governs the formation of chromospheric lines, interpretation of solar chromospheric observations is difficult. The origin and characteristics of many chromospheric features are, because of this, unresolved.
Aims: We focus on studying two prominent features: long fibrils and flare ribbons. To model …
Dissecting bombs and bursts: non-LTE inversions of low-atmosphere reconnection in SST and IRIS observations
Carlsson, M.; Rouppe van der Voort, L. H. M.; de la Cruz Rodríguez, J. +3 more
Ellerman bombs and UV bursts are transient brightenings that are ubiquitously observed in the lower atmospheres of active and emerging flux regions. As they are believed to pinpoint sites of magnetic reconnection in reconfiguring fields, understanding their occurrence and detailed evolution may provide useful insight into the overall evolution of …
The solar chromosphere at millimetre and ultraviolet wavelengths. I. Radiation temperatures and a detailed comparison
De Pontieu, B.; Rezaei, R.; Carlsson, M. +3 more
Solar observations with the Atacama Large Millimeter/submillimeter Array (ALMA) provide us with direct measurements of the brightness temperature in the solar chromosphere. We study the temperature distributions obtained with ALMA Band 6 (in four sub-bands at 1.21, 1.22, 1.29, and 1.3 mm) for various areas at, and in the vicinity of, a sunspot, co…
Semi-empirical model atmospheres for the chromosphere of the sunspot penumbra and umbral flashes
Rouppe van der Voort, Luc; Henriques, Vasco M. J.; Bose, Souvik +1 more
Context. The solar chromosphere and the lower transition region are believed to play a crucial role in the heating of the solar corona. Models that describe the chromosphere (and the lower transition region), accounting for its highly dynamic and structured character are, so far, found to be lacking. This is partly due to the breakdown of complete…