Mesostructure of the solar granulation

Abstract

Quasi-periodic variations in the thermodynamic and hydrodynamic fine-structure properties of the granulation field along the photospheric surface are estimated quantitatively. The darkest vast intergranular lanes, called the intergranular knots, are the most important indicator of their physical properties. The formulated new definitions of “granule” and “intergranular lane” require a revision of the previous results. The definition of mesogranulation is given, and the method of its detection in the granulation field is described. The following important quantitative results, which established the extent and nature of the physical relationship between the granulation and mesogranulation fields, have been obtained for the first time: (1) the intensity amplitude of granules in mesogranules (ΔI(gr)/I ₀)_msgr = +10.3% is a factor of 1.4 larger than that of granules in intermesogranular regions [(ΔI(gr)/I ₀)_imsgr = +7.3%], whereas the intensity amplitude of intergranular lanes in mesogranules [(ΔI(igr)/I ₀)_msgr = −6.0%] is a factor of 1.4 smaller than that of intergranular lanes in intermesogranular regions [(ΔI(igr)/I ₀)_imsgr = −8.4%]; (2) the mean intensities of photospheric granules and intergranular lanes are (ΔI(gr)/I ₀)_phot = +9.2% and (ΔI(igr)/I ₀)_phot = −7.5%, respectively; (3) granules cover 59% of the area of mesogranules, 45% of the area of the photosphere, and 31 % of the area of intermesogranular regions, while intergranular lanes cover 41, 55, and 69% of these areas, respectively; (4) intergranular knots and bright granules virtually never formed and do not exist in mesogranules and intermesogranular regions, respectively; (5) the amplitudes of intensity fluctuations in mesogranules and intermesogranular regions, as well as the areas occupied by them (49.4 and 50.6%, respectively), essentially level off, ΔI(msgr)/I ₀ = +3.6% and ΔI(imsgr)/I ₀ = −3.5%, respectively.