Three-dimensional modeling of the Ca II H&K lines in the solar atmosphere

Abstract

CHROMIS, a new imaging spectrometer at the Swedish 1-m Solar Telescope (SST), can observe the chromosphere in the H and K lines of Ca II at high spatial and spectral resolution. Accurate modeling as well as an understanding of the formation of these lines are needed to interpret the SST/CHROMIS observations. Such modeling is computationally challenging because these lines are influenced by strong departures from local thermodynamic equilibrium, three-dimensional radiative transfer, and partially coherent resonance scattering of photons. We aim to model the CaII H&K lines in 3D model atmospheres to understand their formation and to investigate their diagnostic potential for probing the chromosphere. We model the synthetic spectrum of Ca II using the radiative transfer code Multi3D in three different radiation-magnetohydrodynamic model atmospheres computed with the Bifrost code. We classify synthetic intensity profiles according to their shapes and study how their features are related to the physical properties in the model atmospheres. We investigate whether the synthetic data reproduce the observed spatially-averaged line shapes, center-to-limb variation and compare with SST/CHROMIS images. The spatially-averaged synthetic line profiles show too low central emission peaks, and too small separation between the peaks. The trends of the observed center-to-limb variation of the profiles properties are reproduced by the models. The Ca II H&K line profiles provide a temperature diagnostic of the temperature minimum and the temperature at the formation height of the emission peaks. The Doppler shift of the central depression is an excellent probe of the velocity in the upper chromosphere.

19 pages, 20 figures, accepted for publication by A&A

References in corpus (12)

• CRISP Spectropolarimetric Imaging of Penumbral Fine Structure
• CRISPRED: A data pipeline for the CRISP imaging spectropolarimeter
• On the generation of solar spicules and Alfvénic waves
• Non-equilibrium hydrogen ionization in 2D simulations of the solar atmosphere
• The solar chromosphere at high resolution with IBIS. I. New insights from the Ca II 854.2 nm line
• Non-LTE inversions of the Mg II h&k and UV triplet lines
• 3D Temperature Mapping of Solar Photospheric Fine Structure Using Ca II H Filtergrams
• Atomic data from the Iron Project. LXIV. Radiative transition rates and collision strengths for Ca II
• Heating of the magnetic chromosphere: observational constraints from Ca II 8542 spectra
• Sparse inversion of Stokes profiles. I. Two-dimensional Milne-Eddington inversions
• Reversal-free CaIIH profiles: a challenge for solar chromosphere modeling in quiet inter-network
• On the fine structure of the quiet solar \Ca II K atmosphere

Cited by in corpus (43)

• STiC -- A multi-atom non-LTE PRD inversion code for full-Stokes solar observations
• Three-dimensional modeling of chromospheric spectral lines in a simulated active region
• Dissecting bombs and bursts: non-LTE inversions of low-atmosphere reconnection in SST and IRIS observations
• An observationally-constrained model of strong magnetic reconnection in the solar chromosphere. Atmospheric stratification and estimates of heating rates
• On chromospheric heating during flux emergence in the solar atmosphere
• Temperature constraints from inversions of synthetic solar optical, UV and radio spectra
• Radiation hydrodynamics in simulations of the solar atmosphere
• Observationally based models of penumbral microjets
• A comparative study of two X2.2 and X9.3 solar flares observed with HARPS-N: Reconciling Sun-as-a-star spectroscopy and high-spatial resolution solar observations in the context of the solar-stellar connection
• HAZMAT. VII. The Evolution of Ultraviolet Emission with Age and Rotation for Early M Dwarf Stars
• Center-to-limb variation of spectral lines and continua observed with SST/CRISP and SST/CHROMIS
• Physical properties of bright Ca II K fibrils in the solar chromosphere
• Diagnostic capabilities of spectropolarimetric observations for understanding solar phenomena I. Zeeman-sensitive photospheric lines
• 1.5D NLTE spectral synthesis of a 3D filament/prominence simulation
• Study of the polarization produced by the Zeeman effect in the solar Mg I b lines
• Modeling stellar Ca II H & K emission variations. I. Effect of inclination on the S-index
• Observation of Alfvén Wave Reflection in the Solar Chromosphere: Ponderomotive Force and First Ionization Potential Effect
• Evidence of multithermal nature of spicular downflows. Impact on solar atmospheric heating
• Influence of NLTE effects in Fe I lines on inverted atmosphere II. 6301 A and 6302 A lines formed in 3DNLTE
• Characterization of chromospheric activity based on Sun-as-a-star spectral and disk-resolved activity indices
• Formal Solutions for Polarized Radiative Transfer. IV. Numerical Performances in Practical Problems
• Fast Inversion of Solar Ca II Spectra in Non-Local Thermodynamic Equilibrium
• Chromospheric observations and magnetic configuration of a supergranular structure
• New light on an old problem of the cores of solar resonance lines
• Small-scale magnetic flux emergence preceding a chain of energetic solar atmospheric events
• Magnetic activity of red giants: correlation between the amplitude of solar-like oscillations and chromospheric indicators
• The dynamic chromosphere: pushing the boundaries of observations and models
• Chromospheric emission from nanoflare heating in RADYN simulations
• Formation of H$\epsilon$ in the solar atmosphere
• Investigating the effect of solar ambient and data characteristics on Ca II K observations and line profile measurements
• SunnyNet: A neural network approach to 3D non-LTE radiative transfer
• Probing Na in giant exoplanets with ESPRESSO and 3D NLTE stellar spectra
• Convolutional Neural Networks and Stokes Response Functions
• Observations of umbral flashes in the resonant sunspot chromosphere
• On the center-to-limb variations of the He I 10 830 Å triplet
• The magnetic sensitivity of the Ca II resonance and subordinate lines in the solar atmosphere
• 3D non-LTE Ca II line formation in metal-poor FGK stars. I. Abundance corrections, radial velocity corrections, and synthetic spectra
• Solar Flux Atlases: The new HARPS-N Quiet Sun Benchmark and Ca II H & K Lines Continuum Normalisation
• Three-dimensional non-LTE radiative transfer effects in Fe I lines IV. Line formation at high spatial resolution
• Formation of chromospheric Fe I lines in the near ultraviolet in 1D atmospheres
• EMISSA: Exploring millimetre indicators of solar-stellar activity III. Comparison of Ca II indices and millimetre continua in a 3D model atmosphere
• Accelerated particle beams in a 3D simulation of the quiet Sun. Lower atmospheric spectral diagnostics
• The magnetic sensitivity of the Ca II H and K lines