Abstract
A numerical simulation was performed to interpret high-resolution spectropolarimetric observations of polar faculae on the Sun. A semi-empirical three-dimensional model of facula structures, controlled by several free parameters, was constructed. It consists of two components, the atmosphere within small-scale magnetic flux tubes and the exterior atmosphere. Multi-ray 1.5D radiative transfer calculations were performed along oblique rays passing through a highly inhomogeneous atmosphere of the simulation box. By the comparison of the properties of the calculated Stokes profiles from the synthetic faculae with the observed properties, a set of free parameters of the model (such as: size, number density of flux tubes, internal temperature stratification and magnetic field strength) was deduced, which satisfies the observational constraints. The hypothesis about solar faculae as a conglomerate of small-scale magnetic flux tubes is verified. The model reproduces all observed properties: the continuum contrast and its center-to-limb variation, the Stokes I and V profiles of Fe I and Fe II lines, the apparent magnetic field strengths, and the displacement towards the limb of the continuum intensity against the line-of-sight magnetograms.
Highlights
The polar areas of the Sun take part in the magnetic activity cycle, as do activity regions at low latitudes of the Sun
The latter depends on the merging height, which in turn depends on the number density of magnetic flux tubes (MFTs) on the surface, or number of tubes in the simulation box
We have introduced the filling factor of the model fmod defined as the ratio of the area occupied by the flux tubes at z = 0 km to the total area of the simulation box: fmod πR20NMFT · S box Distribution NMFT in the box fmod
Summary
The polar areas of the Sun take part in the magnetic activity cycle, as do activity regions at low latitudes of the Sun. For the successful study of such small-scale magnetic structures close to the solar limb one has to combine high spectral and spatial resolution spectropolarimetric observations with efficient methods of data analysis and interpretation including numerical simulations. Kneer: Modeling of polar faculae on the Sun integration path) are used for adjustment of the guess model This peculiarity of the method makes it difficult to apply it to problems where the atmosphere along the LOS is very irregular and high coverage with grid points is mandatory. Keller et al (2004) have used the MURaM code of the Lindau-Chicago group (Vögler & Schüssler 2003; Vögler et al 2005), which solves numerically the complete set of the time-dependent magneto-hydrodynamic equations together with non-gray radiative transfer They obtained good agreement with the observations of solar faculae by Lites et al (2004).
Sign-in/Register to view highlights & summary Talk to us
Join us for a 30 min session where you can share your feedback and ask us any queries you have
Schedule a callDisclaimer: All third-party content on this website/platform is and will remain the property of their respective owners and is provided on "as is" basis without any warranties, express or implied. Use of third-party content does not indicate any affiliation, sponsorship with or endorsement by them. Any references to third-party content is to identify the corresponding services and shall be considered fair use under The CopyrightLaw.
