NESSY: NLTE spectral synthesis code for solar and stellar atmospheres

¹ Astrophysics Group, Imperial College London, London SW7 2AZ, UK
e-mail: tagirovrinat@gmail.com
² Institute for Astronomy, ETH Zürich, 8093 Zurich, Switzerland
³ Physical Meteorological Observatory Davos, 7260 Davos Dorf, Switzerland
⁴ Max Planck Institute for Solar System Research, 37077 Göttingen, Germany

Received: 22 March 2016
Accepted: 20 February 2017

Abstract

Context. Physics-based models of solar and stellar magnetically-driven variability are based on the calculation of synthetic spectra for various surface magnetic features as well as quiet regions, which are a function of their position on the solar or stellar disc. Such calculations are performed with radiative transfer codes tailored for modeling broad spectral intervals.

Aims. We aim to present the NLTE Spectral SYnthesis code (NESSY), which can be used for modeling of the entire (UV-visible-IR and radio) spectra of solar and stellar magnetic features and quiet regions.

Methods. NESSY is a further development of the COde for Solar Irradiance (COSI), in which we have implemented an accelerated Λ-iteration (ALI) scheme for co-moving frame (CMF) line radiation transfer based on a new estimate of the local approximate Λ-operator.

Results. We show that the new version of the code performs substantially faster than the previous one and yields a reliable calculation of the entire solar spectrum. This calculation is in a good agreement with the available observations.