High-resolution solar spectral irradiance from extreme ultraviolet to far infrared

Abstract

[1] This paper presents new extremely high-resolution solar spectral irradiance (SSI) calculations covering wavelengths from 0.12 nm to 100 micron obtained by the Solar Irradiance Physical Modeling (SRPM) system. Daily solar irradiance spectra were constructed for most of Solar Cycle 23 based on a set of physical models of the solar features and non-LTE calculations of their emitted spectra as function of viewing angle, and solar images specifying the distribution of features on the solar disk. Various observational tests are used to assess the quality of the spectra provided here. The present work emphasizes the effects on the SSI of the upper chromosphere and full-non-LTE radiative transfer calculation of level populations and ionizations that are essential for physically consistent results at UV wavelengths and for deep lines in the visible and IR. This paper also considers the photodissociation continuum opacity of molecular species, e.g., CH and OH, and proposes the consideration of NH photodissociation which can solve the puzzle of the missing near-UV opacity in the spectral range of the near-UV. Finally, this paper is based on physical models of the solar atmosphere and extends the previous lower-layer models into the upper-transition-region and coronal layers that are the dominant source of photons at wavelengths shorter than ∼50 nm (except for the He II 30.4 nm line, mainly formed in the lower-transition-region).

The Ni I lines in the solar spectrum

“…Figure 1 shows a comparison between several line profiles along the spectra with increasing wavelength. With solid lines we indicate our calculation, with dashed lines the spectra calculated by Fontenla et al (2011) present only in the visible lines, and with doted lines the observations. The differences between the two synthetic profiles are in the NLTE calculations.…”

“…In our case the populations were calculated in full NLTE with 61 levels. The spectra calculated by Fontenla et al (2011) considered NLTE calculation only for 10 levels, and then they approximated the departure coefficients of the rest of the levels with the value obtained for the last level calculated in NLTE.…”

“…The populations for the different neutral atoms and ions were calculated in full NLTE. The atomic species taken into account were that from Table 2 in Fontenla et al (2011), and the only change included was the new Ni I atomic model that increased the number of energy levels from 10 to 61.…”

“…We used the latest semi-empirical models built by Fontenla et al (2011) for features observed on the solar disk. These features were defined by their emitted intensity in Ca II K images taken with Precision Photometric Solar Telescope (PSPT) at Osservatorio Astronomico di Roma (Fontenla et al 2009).…”

“…To take into account the strong Ni I lines in the near UV range we increased the number of energy levels in the atomic model, and update the atomic data to calculate 94 M. C. Vieytes, P. J. D. Mauas & J. M. Fontenla the populations in full NLTE using the latest available semi-empirical models for the Solar atmosphere (Fontenla et al 2011).…”