Structure of solar faculae

In solar facular regions (plages), three distinct classes of magnetic features are observed: small-scale flux tubes, knots, and pores. Small flux tubes have granular scales; they are in constant motion and can well be simulated numerically according to the concept of magneto-convection. On this dynamic background, one observes quite stable, long-lived. and bright objects called facular knots, with a diameter of 3-8 mm and fine (less than 1 mm) inner filamentary structure. Their magnetic field strength varies in the range from 250 to 1200 G. Our present paper considers only these active formations. The stationary MHD problem is solved and analytical formulae are derived for calculation of the pressure, density, temperature, and Alfven Mach number in the studied configuration from the corresponding magnetic field structure. The facular knot is modelled in a hydrostatic atmosphere defined by the Avrett & Loeser model (2008) and is surrounded by a weak (2 G) external field corresponding to the average global magnetic field strength on the solar surface. The constructed 3D analytical model presents the facular knot as a magnetic `fountain' with numerous slender fibrils and allows solving the following tasks: 1. Calculation of temperature profiles of the knot at any height of the atmosphere; 2. Description of ring brightening and fine azimuthal fibril structure observed in plages at high spatial resolution; 3. New interpretation of Centre-to-Limb Variation problem that fits well with the observational data.