Related papers: Fast inversion of solar Ca II spectra
Context. The radiative losses in the solar chromosphere vary from 4~kW~m$^{-2}$ in the quiet Sun, to 20~kW~m$^{-2}$ in active regions. The mechanisms that transport non-thermal energy to and deposit it in the chromosphere are still not…
Non-local thermodynamical equilibrium (non-LTE) line formation for neutral and singly-ionized iron is considered through a range of spectral types when the effective temperature varies from 6500 K up to 8500 K, the gravity from log g = 4…
We study the C8.4 class solar flare SOL2016-05-14T11:34 UT using high-resolution spectral imaging in the Ca ii 8542 {\AA} line obtained with the CRISP imaging spectropolarimeter on the Swedish 1-m Solar Telescope. Spectroscopic inversions…
Obtaining the magnetic field vector accurately in the solar atmosphere is essential for studying changes in field topology during flares and to reliably model space weather. We tackle this problem by applying various inversion methods to a…
Chromospheric inferences rely on the interpretation of spectral lines that are formed under Non-Local Thermodynamic Equilibrium (NLTE) conditions. In the presence of oscillations, changes in the opacity impact the response height of the…
The Milne-Eddington approximation provides an analytic and simple solution to the radiative transfer equation. It can be easily implemented in inversion codes that are used to fit spectro-polarimetric observations to infer average values of…
Non-local thermodynamic equilibrium (non-LTE) line formation for Ca I-Ca II, Ti I-Ti II, and Fe I-Fe II is considered in model atmospheres of giant stars with an effective temperature of 4000 K $\le$ Teff $\le$ 5000 K and a metal abundance…
Context. The solar irradiance is known to change on time scales of minutes to decades, and it is suspected that its substantial fluctua- tions are partially responsible for climate variations. Aims. We are developing a solar atmosphere code…
Modeling the variability of the solar spectral irradiance is a key factor for understanding the solar influence on the climate of the Earth. As a first step to calculating the solar spectral irradiance variations we reproduce the solar…
Aims. We examined the capabilities of methods based on the weak-field approximation and line bisectors to extract fast and reliable information about the height stratification of the magnetic field and line-of-sight velocities,…
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…
We study a solar spicule observed off-limb using high-resolution imaging spectroscopy in the Ca II 8542 \AA\ line obtained with the CRisp Imaging SpectroPolarimeter (CRISP) on the Swedish 1-m Solar Telescope. Using a new version of the…
Context. The pursuit of more realistic spectroscopic modelling and consistent abundances has led us to begin a new series of papers designed to improve current solar and stellar abundances of various atomic species. To achieve this, we have…
A very slight rotation-induced latitudinal temperature variation (presumably on the order of several Kelvin) on the solar surface is theoretically expected. While recent high-precision solar brightness observations reported its detection,…
A comprehensive model atom for Fe with more than 3000 energy levels is presented. As a test and first application of this model atom, Fe abundances are determined for the Sun and five stars with well determined stellar parameters and…
Quantitative thermodynamical, dynamical and magnetic properties of the solar and stellar plasmas are obtained by interpreting their emergent non-polarized and polarized spectrum. This inference requires the selection of a set of spectral…
When inverting solar spectra, image degradation effects that are present in the data are usually approximated or not considered. We develop a data reduction method that takes these issues into account and minimizes the resulting errors. By…
The \ion{Fe}{i} lines observed by the Hinode/SOT spectropolarimeter were always seen in absorption, apart from the extreme solar limb. Here we analyse a unique dataset capturing these lines in emission during a solar white-light flare. We…
In this paper we propose an inversion strategy for the analysis of spectropolarimetric measurements taken by {\em Hinode} in the quiet Sun. The spectropolarimeter of the Solar Optical Telescope aboard {\em Hinode} records the Stokes spectra…
The Ca II 854.2 nm spectral line is a common diagnostic of the solar chromosphere. The average line profile shows an asymmetric core, and its bisector shows a characteristic inverse-C shape. The line actually consists of six components with…