Quiet-Sun hydrogen Lyman-alpha line profile derived from SOHO/SUMER solar-disk observations

Abstract

The solar radiation in the Lyman-alpha spectral line of hydrogen plays a significant role in the illumination of chromospheric and coronal structures, such as prominences, spicules, chromospheric fibrils, cores of coronal mass ejections, and solar wind. Moreover, it is important for the investigation of the heliosphere, Earth's ionosphere, and the atmospheres of planets, moons, and comets. We derive a reference quiet-Sun Lyman-alpha spectral profile that is representative of the Lyman-alpha radiation from the solar disk during a minimum of solar activity. This profile can serve as an incident radiation boundary condition for the radiative transfer modelling of chromospheric and coronal structures. Because the solar radiation in the Lyman lines is not constant over time but varies significantly with the solar cycle, we provide a method for the adaptation of the incident radiation Lyman line profiles (Lyman-alpha and higher lines) to a specific date. Moreover, we analyse how the change in the incident radiation influences the synthetic spectra produced by the radiative transfer modelling. To take into account the Lyman-alpha variation with the solar cycle, we used the LISIRD composite Lyman-alpha$ index. To estimate the influence of the change in the incident radiation in the Lyman lines on the results of radiative transfer models, we used a 2D prominence fine structure model. The analysis of the influence of the change in the incident radiation shows that the synthetic spectra are strongly affected by the modification of the incident radiation boundary condition. The hydrogen H alpha line can also be considerably affected, despite the fact that the H alpha radiation from the solar disk does not vary with the solar cycle.

arXiv comment17 pages, 7 figures, 2 appendices (A, B), to be published in Astronomy and Astrophysics

References in corpus (15)

• The Solar Cycle
• Solar parameters for modeling interplanetary background
• PORTA: A three-dimensional multilevel radiative transfer code for modeling the intensity and polarization of spectral lines with massively parallel computers
• The LYRA Instrument Onboard PROBA2: Description and In-Flight Performance
• Discovery of Scattering Polarization in the Hydrogen Lyman-$\alpha$ Line of the Solar Disk Radiation
• A Survey of Water Production in 61 Comets from SOHO/SWAN Observations of Hydrogen Lyman-alpha: Twenty-One Years 1996-2016
• The Ly-alpha profile and center-to-limb variation of the quiet Sun
• Evolution of the Solar Lyman-Alpha line profile during the solar cycle
• Radiation hydrodynamics in simulations of the solar atmosphere
• Hydrogen Lyman-alpha and Lyman-beta spectral radiance profiles in the quiet Sun
• Electron production by solar Ly-α line radiation in the ionospheric D-region
• IRIS Mg II Observations and Non-LTE Modeling of Off-limb Spicules in a Solar Polar Coronal Hole
• 2D non-LTE modelling of a filament observed in the H_alpha line with the DST/IBIS spectropolarimeter
• Hydrogen Lyman-alpha and Lyman-beta radiances and profiles in polar coronal holes
• Stability of the interstellar hydrogen inflow longitude from 20 years of SOHO/SWAN observations

Cited by in corpus (7)

• Intrinsic Lyman alpha Profiles of High-Velocity G, K, and M Dwarfs
• Center-to-limb variation of spectral lines and continua observed with SST/CRISP and SST/CHROMIS
• Combining White Light and UV Lyman-alpha Coronagraphic Images to determine the Solar Wind Speed: the Quick Inversion Method
• Effects of the chromospheric Lyα line profile shape on the determination of the solar wind HI outflow velocity using the Doppler dimming technique
• Full non-LTE spectral line formation I. Setting the stage
• On the center-to-limb variations of the He I 10830 Å triplet
• The diversity of spectral shapes of hydrogen Lyman lines and Mg II lines in a quiescent prominence