Astronomical Institute of the Academy of Sciences of the Czech Republic
Postal address: CZ 25165, Ondrejov, The Czech Republic
e-mail: pambroz@asu.cas.cz
Global and Large-Scale Dynamic Properties of the Sun
The process of solar convection can only be partly observed in the solar photosphere, mainly by means of the best detectable velocities of small-scale convective elements, created in the upper part of the convection zone. The lower part of the convection zone, with dominant influence on the dynamo action, is, according to theoretical models, occupied by large-scale convective elements (cells), probably playing a substantial role in the maintenance of latitudinal dependent differential rotation. Observations indicated the presence of giant cells, but these have not been confirmed sufficiently yet. The purpose of our investigations is to identify the position of the giant cells, and to determine the velocity structure, the characteristic dimensions, the relation to the magnetic field structure and to the distribution of active phenomena. A new method of 2D detection of horizontal transport velocities of the magnetized plasma has been developed, and the project of testing our results using other measurements in international collaborations with Austrian and French scientists has been continued.
Recent results
The large-scale solar convection has been analyzed using time variations of photospheric magnetic flux redistribution on the base of two different sets of observations in the coarse of two last cycles of solar activity. The inferred horizontal flow structure in the solar photosphere was found to depend strongly on the spatial resolution of the fundamental observations of magnetic structures, as well as on the averaging procedure used in data processing. The large-scale convective cells were identified, and selective velocities for different solar active phenomena were found. The identification of the cellular structure of large-scale convection is the most recent step in determining solar global velocity parameters. The long-term zonal averaging of the derived velocities explains global characteristics in terms of differential rotation or meridional circulation, directly supported by theoretical models.
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