English
Related papers

Related papers: Solar BaII 4554 A line as Doppler diagnostics: NLT…

200 papers

The purpose of this paper is to characterize the statistical properties of solar granulation in the photosphere and low chromosphere up to 650 km. We use velocity and intensity variations obtained at different atmospheric heights from…

Solar and Stellar Astrophysics · Physics 2015-05-14 R. Kostik , E. Khomenko , N. Shchukina

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,…

Solar and Stellar Astrophysics · Physics 2025-03-18 A. L. Siu-Tapia , L. R. Bellot Rubio , D. Orozco Suárez

The measurement of Doppler velocities in spectroscopic solar observations requires a reference for the local frame of rest. The rotational and radial velocities of the Earth and the rotation of the Sun introduce velocity offsets in the…

Solar and Stellar Astrophysics · Physics 2015-05-27 Jaime de la Cruz Rodríguez , Dan Kiselman , Mats Carlsson

The Solar Dynamics Observatory/Helioseismic and Magnetic Imager (SDO/HMI) filtergrams, taken at six wavelengths around the Fe I 6173.3 {\AA} line, contain information about the line-of-sight velocity over a range of heights in the solar…

The current analysis is dedicated to a detailed investigation of the non-Local Thermodynamic Equilibrium (NLTE) effects influencing the formation of the Fe I 6173 A line, which is widely used by many instruments including the Helioseismic…

Solar and Stellar Astrophysics · Physics 2023-01-25 H. N. Smitha , M. van Noort , S. K. Solanki , J. S. Castellanos Durán

Understanding the dynamics of the solar chromosphere is crucial to understanding energy transport across the solar atmosphere. The chromosphere is optically thick at many wavelengths and described by non-local thermodynamic equilibrium…

Solar and Stellar Astrophysics · Physics 2019-01-30 Jeffrey W. Reep , Stephen J. Bradshaw , Nicholas A. Crump , Harry P. Warren

The observed solar photospheric magnetic fields and Doppler velocities are frequently used to quantify the Poynting flux and helicity flux. Multiple methods have been developed for this purpose, but their estimates of the Poynting flux and…

Solar and Stellar Astrophysics · Physics 2026-04-20 Jiayi Liu , Xudong Sun , Peter W. Schuck , Lars K. S. Daldorff

In this paper, the physical conditions within the inhomogeneous solar atmosphere have been reconstructed by means of solving the inverse problem of Non Local Thermodynamic Equilibrium (NLTE) radiative transfer. The profiles of…

Astrophysics · Physics 2008-11-26 M. I. Stodilka , S. Z. Malynych

We explored the impact that Doppler dimming and brightening effects from bulk motions of solar prominences have on the formation of Lya, Ha, and MgII h line profiles. We compared two schemes in which these effects manifest; when the…

Solar and Stellar Astrophysics · Physics 2024-06-21 Aaron W. Peat , Christopher M. J. Osborne , Petr Heinzel

Realistic ab-initio 3D, radiative-hydrodynamical convection simulations of the solar granulation have been applied to FeI and FeII line formation. In contrast to classical analyses based on hydrostatic 1D model atmospheres the procedure…

Astrophysics · Physics 2007-05-23 M. Asplund , AA. Nordlund , R. Trampedach , C. Allende Prieto , R. F. Stein

Ultraviolet over-ionisation of iron atoms in the solar atmosphere leads to deviations in their level populations from the Saha-Boltzmann statistics. This causes their line profiles to form in Non-Local Thermodynamic Equilibrium (NLTE)…

Solar and Stellar Astrophysics · Physics 2020-01-29 H. N. Smitha , R. Holzreuter , M. van Noort , S. K. Solanki

Observations of the dynamics of solar coronal structures are necessary to investigate space weather phenomena and global heating of the corona. The profiles of high temperature lines emitted by the hot plasma are usually integrated by…

Solar and Stellar Astrophysics · Physics 2021-10-27 J. -M. Malherbe , P. Mein , F. Sayede , P. Rudawy , K. Phillips , F. Keenan , J. Rybak

Non-local thermodynamic equilibrium (NLTE) effects in diagnostically important solar Fe I lines are important due to the strong sensitivity of Fe I to ionizing UV radiation, which may lead to a considerable under-population of the Fe I…

Solar and Stellar Astrophysics · Physics 2015-10-21 René Holzreuter , Sami K. Solanki

The astrophysically very interesting Li I 671 nm line has been observed with high spatial resolution in solar granulation with the intention to diagnose departures from local thermodynamic equilibrium (LTE) in the line formation. The…

Astrophysics · Physics 2007-05-23 Dan Kiselman

We test our knowledge of the atomic opacity in the solar UV spectrum. Using the atomic data compiled in Paper I from modern, publicly available, databases, we perform calculations that are confronted with space-based observations of the…

Astrophysics · Physics 2009-11-07 C. Allende Prieto , I. Hubeny , D. L. Lambert

Convective motions in solar-type stellar atmospheres induce Doppler shifts that affect the strengths and shapes of spectral absorption lines and create slightly asymmetric line profiles. 1D LTE studies of elemental abundances are not able…

Solar and Stellar Astrophysics · Physics 2018-10-10 G. Harutyunyan , M. Steffen , A. Mott , E. Caffau , G. Israelian , J. I. González Hernández , K. G. Strassmeier

The Helioseismic and Magnetic Imager (HMI) onboard the Solar Dynamics Observatory (SDO) is designed to study oscillations and the mag- netic field in the solar photosphere. It observes the full solar disk in the Fe I absorption line at…

Solar and Stellar Astrophysics · Physics 2015-05-28 Bernhard Fleck , Sebastien Couvidat , Thomas Straus

Doppler orbitography uses the Doppler shift in a transmitted signal to determine the orbital parameters of satellites including range and range-rate (or radial velocity). We describe two techniques for atmospheric-limited optical Doppler…

Instrumentation and Methods for Astrophysics · Physics 2020-06-09 Benjamin P. Dix-Matthews , Sascha W. Schediwy , David R. Gozzard , Simon Driver , Karl Ulrich Schreibe , Randall Carman , Michael Tobar

The possibility of significant systematic errors due to the use of 1D homogeneous atmospheres in lithium-abundance determinations of cool stars motivates a study of non-local-thermodynamic-equilibrium (NLTE) effects on Li I line formation…

Astrophysics · Physics 2009-10-30 Dan Kiselman

Many promising explosion models for the elusive origin of Type Ia supernovae (SNe Ia) ultimately fail to completely reproduce a number of observed properties of these events. One limiting factor for many of these models is the use of the…

High Energy Astrophysical Phenomena · Physics 2025-05-19 Samuel J. Boos , Luc Dessart , Ken J. Shen , Dean M. Townsley
‹ Prev 1 2 3 10 Next ›