A formation mechanism of magnetic elements in regions of mixed polarity

We present 2-D, fully compressible radiation-MHD simulations of the solar photospheric and subphotospheric layers that run for 2 hours of solar time starting from a magnetic configuration with mixed polarities. In the atmospheric layers the simulation reveals a correlation between field strength and inclination, with a nearly vertical strong-field magnetic component and a more horizontal weak-field component, in agreement with the observations. Our simulation also shows that magnetic flux is converted from one of these states to the other. In particular, magnetic flux sheets can also be formed when a new downflow lane starts due to granule fragmentation. The dynamics of the granulation and field-line reconnection are found to play a role in the initial stages of a magnetic element's formation. The simulation predicts that during or shortly after their formation magnetic elements could be associated with oppositely polarized flux at a small spatial scale.     

Modeling of convective motions in the envelope of procyon. II. Asymmetry of the spectral lines

Principal Astronomical Observatory, Ukrainian Academy of Sciences. Translated from Astrofizika, Vol. 31, No. 3, pp. 589–600, November–December, 1989.     

Artificial granules in 2-D solar models

Two-dimensional, hydrodynamic, time-dependent models of solar granulation have been used to determine characteristics of artificial granules. It is found that the evolution of granules which subsequently fragment, respectively disappear, is fundamentally different. Dissolution of artificial granules is the basic process (48%–58%) in 2-D models. The number of small-scale and short-lived granules increases continuously toward the smaller scales. The main contributor to the total area are the granules with sizes about 900–1000 km. The mean lifetime of artificial granules is estimated to be 6–11 min.     

Power spectra of artificial granulation

Two-dimensional, non-stationary hydrodynamic models of solar granulation with gray and non-gray atmospheres have been used to obtain spatial, temporal, and spatio-temporal power spectra. The temperature, density of kinetic energy, monochromatic intensity, integrated flux, and vertical velocity spectra have been studied for a comparison with the Kolmogorov power law as well as for a qualitative understanding of oscillations, which are reproduced as a result of modelling.     

Iron abundance and microturbulence in Arcturus,Canopus, α Cen A,and Sun from FeI and FeII lines

The iron abundance and microturbulent velocities in Arcturus, Canopus, and α CenA have been determined from Fel and Fell lines relative to the Sun. α CenA is found to have an enhanced iron abundance, while Canopus and Arcturus are found to have a deficiency of iron. The behaviour of the determined microturbulent velocities is discussed.     

Evolution of solar magnetic tubes from observations of Stokes parameters

Basic scenarios and mechanisms for the formation and decay of small-scale magnetic elements and their manifestation in synthesized Stokes profiles of the Fe I 15648.5 Å infrared line are considered in the context of two-dimensional modeling of nonstationary magnetogranulation on the Sun. The stage of convective collapse is characterized by large redshifts in the V profiles accompanied by complete Zeeman splitting of the I profiles. This is due to intense downward flows of material, which facilitates the concentration of longitudinal field with an amplitude of about several kG in the tube. The dissipation of strong magnetic structures is characterized by blueshifts in their profiles, which result from upward fluxes that decrease the magnetic field in the tube. Typical signatures during key stages in the evolution of compact magnetic elements should be detectable via observations with sufficiently high spatial and temporal resolution.