Semi-empirical model atmospheres for the chromosphere of the sunspot penumbra and umbral flashes

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 frequency redistribution (CRD) in the chromospheric layers and also because of the difficulty in obtaining complete sets of observations that adequately constrain the solar atmosphere at all relevant heights. Aims. We aim to obtain semi-empirical model atmospheres that reproduce the features of the Mg II h&k line profiles that sample the middle chromosphere with focus on a sunspot. Methods. We used spectropolarimetric observations of the Ca II 8542 Å spectra obtained with the Swedish 1 m Solar Telescope and used NICOLE inversions to obtain semi-empirical model atmospheres for different features in and around a sunspot. These were used to synthesize Mg II h&k spectra using the RH1.5D code, which we compared with observations taken with the Interface Region Imaging Spectrograph (IRIS). Results. Comparison of the synthetic profiles with IRIS observations reveals that there are several areas, especially in the penumbra of the sunspot, where most of the observed Mg II h&k profiles are very well reproduced. In addition, we find that supersonic hot down-flows, present in our collection of models in the umbra, lead to synthetic profiles that agree well with the IRIS Mg II h&k profiles, with the exception of the line core. Conclusions. We put forward and make available four semi-empirical model atmospheres. Two for the penumbra, reflecting the range of temperatures obtained for the chromosphere, one for umbral flashes, and a model representative of the quiet surroundings of a sunspot.

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Effects of Ambipolar Diffusion on Prominence Thread Models

International Astronomical Union Colloquium ◽

10.1017/s0252921100025513 ◽

1994 ◽

Vol 144 ◽

pp. 315-321 ◽

Cited By ~ 1

Author(s):

M. G. Rovira ◽

J. M. Fontenla ◽

J.-C. Vial ◽

P. Gouttebroze

Keyword(s):

Energy Balance ◽

Transition Region ◽

Ambipolar Diffusion ◽

Line Profiles ◽

Balance Equations ◽

Model Calculations ◽

Partial Frequency ◽

Frequency Redistribution ◽

Partial Frequency Redistribution ◽

Theoretical Structure

AbstractWe have improved previous model calculations of the prominence-corona transition region including the effect of the ambipolar diffusion in the statistical equilibrium and energy balance equations. We show its influence on the different parameters that characterize the resulting prominence theoretical structure. We take into account the effect of the partial frequency redistribution (PRD) in the line profiles and total intensities calculations.

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Diagnostics of Non-thermal Particles in Solar Chromospheric Flares

Symposium - International Astronomical Union ◽

10.1017/s0074180900182087 ◽

2004 ◽

Vol 219 ◽

pp. 171-175

Author(s):

C. Fang ◽

Z. Xu ◽

M. D. Ding

Keyword(s):

Total Energy ◽

Energy Flux ◽

Atmospheric Condition ◽

Particle Beam ◽

Profile Measurement ◽

Solar Chromosphere ◽

Line Profiles ◽

Total Energy Flux ◽

Hydrogen Lines ◽

Semi Empirical

Particle beam bombardment on the solar chromosphere produces non-thermal ionization and excitation. The effect on hydrogen lines is investigated by using non-LTE theory and semi-empirical flare models. It has been found that in the case of electron bombardment, the Hα line is widely broadened and enhanced. Significant enhancements at the wings of Lyα and Lyβ lines are also predicted. In the case of proton bombardment, less strong broadening and less central reversal are expected. We found that the total energy flux of the particle beam and the atmospheric condition give much influence on the line profiles, which, however, are less sensitive to the power index. Based on the Hα line profile measurement, a method to deduce the total energy flux of the particle beam is proposed.

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Study of CO line profiles in molecular clouds - Relaxing the assumption of complete frequency redistribution

The Astrophysical Journal ◽

10.1086/160278 ◽

1982 ◽

Vol 260 ◽

pp. 579 ◽

Cited By ~ 1

Author(s):

S. Deguchi ◽

J. Kwan

Keyword(s):

Molecular Clouds ◽

Line Profiles ◽

Frequency Redistribution ◽

Complete Frequency

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Hydrogen Line Profiles

Highlights of Astronomy ◽

10.1017/s1539299600011564 ◽

1995 ◽

Vol 10 ◽

pp. 411-414 ◽

Cited By ~ 1

Author(s):

I. Hubeny

Keyword(s):

Transfer Problem ◽

Current Status ◽

Line Profiles ◽

Line Broadening ◽

Hydrogen Line ◽

Radiative Transfer Problem ◽

Frequency Redistribution ◽

Sufficient Detail ◽

High Degree ◽

Complete Frequency

Observed hydrogen line profiles are an enormously important source of diagnostic information about virtually all kinds of astronomical bodies. Therefore, it is important to understand the hydrogen line formation in sufficient detail to be able to achieve a high degree of reliability by analyzing observed hydrogen line profiles.Calculation of the predicted hydrogen line profiles involves two basic ingredients, (i) intrinsic line profiles, or line broadening - ”atomic physics” part, and (ii) the radiative transfer problem - ”astrophysics” part. There is not enough space to discuss here the current status of the astrophysical part of the problem. Fortunately, this topic is covered by many reviews. There are two major problems here, (a) departures from local thermodynamic equilibrium (LTE) - the so-called non-LTE description (e.g. Mihalas 1978; Hubenyet al.1994); and (b) departures from complete frequency redistribution (Cooperet al.1989; Hubeny and Lites 1994).

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Non-Maxwellian Analysis of the Transition-region Line Profiles Observed by theInterface Region Imaging Spectrograph

The Astrophysical Journal ◽

10.3847/1538-4357/aa71a8 ◽

2017 ◽

Vol 842 (1) ◽

pp. 19 ◽

Cited By ~ 12

Author(s):

Jaroslav Dudík ◽

Vanessa Polito ◽

Elena Dzifčáková ◽

Giulio Del Zanna ◽

Paola Testa

Keyword(s):

Transition Region ◽

Line Profiles ◽

Imaging Spectrograph ◽

Region Line

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A Semi-Empirical Model for Predicting Frost Properties

Processes ◽

10.3390/pr9030412 ◽

2021 ◽

Vol 9 (3) ◽

pp. 412

Author(s):

Shao-Ming Li ◽

Kai-Shing Yang ◽

Chi-Chuan Wang

Keyword(s):

Thermal Conductivity ◽

Linear Programming ◽

Numerical Model ◽

Empirical Model ◽

Quantitative Method ◽

Predictive Ability ◽

Dimensionless Temperature ◽

Crystal Shape ◽

Proposed Model ◽

Semi Empirical

In this study, a quantitative method for classifying the frost geometry is first proposed to substantiate a numerical model in predicting frost properties like density, thickness, and thermal conductivity. This method can recognize the crystal shape via linear programming of the existing map for frost morphology. By using this method, the frost conditions can be taken into account in a model to obtain the corresponding frost properties like thermal conductivity, frost thickness, and density for specific frost crystal. It is found that the developed model can predict the frost properties more accurately than the existing correlations. Specifically, the proposed model can identify the corresponding frost shape by a dimensionless temperature and the surface temperature. Moreover, by adopting the frost identification into the numerical model, the frost thickness can also be predicted satisfactorily. The proposed calculation method not only shows better predictive ability with thermal conductivities, but also gives good predictions for density and is especially accurate when the frost density is lower than 125 kg/m3. Yet, the predictive ability for frost density is improved by 24% when compared to the most accurate correlation available.

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