Sergey A. Baban
Scientist at the Russian Federal Nuclear Center - All-Russian Scientific Research Institute of Technical Physics (RFNC-VNIITF)
Project Scientific Leader:
Prof. Andrey N. Starostin, Dr. of science
Head of department at the State Research Center of Russian Federation - Troitsk Institute for Innovation and Fusion Research (SRC TRINITI)
Subproject Leader at SRC TRINITI:
Yury V. Petrushevich, Dr. of science
Head of laboratory at the State Research Center of Russian Federation - Troitsk Institute for Innovation and Fusion Research (SRC TRINITI)
Subproject Leader at SAI-MSU:
Vladimir A. Baturin, Ph. D
Senior scientist at the P.K. Sternberg State Astronomical Institute M.V.Lomonosov Moscow State University (SAI-MSU)
Foreign collaborating institutions
Information about the project
In modern astrophysics the model of the Sun is understood as a simulation of how the distribution of solar plasma chemical composition evolves in time starting from the initial homogeneous stage until the modern state of the Sun. A detailed description of the evolution of the Sun is necessary for realistic forecasting of processes on the Earth and in the solar system. That is because the structure and evolution of the Sun determine the chemical composition of the planets, as well as their formation conditions and further evolution. The change of macroscopic parameters of the Sun during the evolution (brightness and radius growth, the surface temperature change, a possibility of non-steady evolution stages) determines the whole fortune of the solar system bodies.
The standard model of the solar interior was formed by the mid of the 20th century and was widely recognized until the late 80s. It was based on some substantially simplified assumptions. For example, it was deemed sufficient to consider evolution of only the basic components such as hydrogen and helium that could be transformed through thermonuclear reactions localized in the solar core. At the same time it was assumed that all intermediate components of the transformation chain were in equilibrium, i.e. all reactions were considered as single-stage ones. However, recently obtained extensive data of observations on the eigenfrequencies of solar vibrations provide substantial information about solar internal environment. These data are highly accurate and allow one to obtain the profiles of the acoustic speed and solar density. Therefore those data provide a possibility to calculate physical conditions in the solar interior, and, as a result, to improve the standard model of the Sun: presently the deviation of theoretical and measured frequencies exceeds the experimental accuracy by one-two orders of magnitude.
The objective of the project is to create a refined model of the Sun on the basis of recent achievements in description of weakly non-ideal plasma and related processes using the up-to-date helioseismic experimental data.
Development of the model of the Sun being suggested includes the creation of the most accurate model of the solar-plasma equation of state (EOS), refinement of data on opacities and energy-release rates at various stages of the solar chemical evolution, incorporation of turbulent mixing models to describe convective energy and mass transport, as well as the inclusion of the processes of diffusion and separation of heavy elements, essentially effecting the chemical elements distribution along the radius of the Sun.
The participating institutions have created special-purpose program packages to calculate complex hydrodynamic processes including diffusion and matter segregation, as well as thermodynamic properties and opacities of plasmas of various chemical compositions. Those program packages have also been complemented with physical and numerical models developed to describe kinetic processes and composition variations due to thermonuclear burn under the conditions of solar plasma. Project participants are recognized as high-level experts in the appropriate fields of research.
The objective of the project is being implemented by adaptation of existing radiation-hydrodynamics code packages to the solar plasma conditions which would enable to model appropriate physical processes in solar plasma and to estimate influence of refinements performed on the final model of the Sun. As a result, the model of chemical evolution of nonideal plasma of the Sun will be created with the account of recommendations elaborated at the previous stages of activities along with the verification of physical models on the base of analysis of helioseismic data.
Improvement of the description of the physical phenomena and processes in the solar plasma is based on published helioseismological data on the solar acoustic speed and density profiles. The dependence of multicomponent composition along the radius of the Sun is taken into account to improve the EOS of weakly non-ideal solar plasma. The obtained EOS will be compared to the previously published theoretical data. To correctly describe radiation transfer processes, it is supposed to use improved opacity data reflecting the radial change of plasma chemical and ionic composition. The improvement of the opacity data is based on detailed description of atomic structure and spectra for the whole scope of bound-bound and bound-free transitions with adequate account for plasma effects. To describe the regions of convective transfer, the semi-empirical k-ε model of turbulent intermixing is employed. The parameters of this model are being adjusted using the data of laboratory experiments and direct numerical simulations. While the previous models were intended to calculate the width of the convective transfer zone, the new model is expected to allow determining the boundary of this zone in a self-consistent way. The processes of diffusion and separation of heavy elements in the gravitational field will also be considered. Those processes are important for adequate description of chemical elements distribution along the radius of the Sun, and, hence, for calculating more accurate EOS and opacities. In addition, expressions for the fusion reactions rates will be corrected for the fast-particle contribution.
The data obtained will provide the description of the current condition of the Sun and its evolution. The expected results will provide the ground to analyze the effects of the considered physical parameters on the final model along with the physical-quantity distribution inside the Sun.
Implementation of the project will give the possibility not only to improve the standard model of the Sun, but also to develop up-to-date theoretical models in the physics of non-ideal plasma altogether. As a result, theoretical and numerical models will be created to describe physical parameters of weakly non-ideal plasmas with a multiparameter chemical composition. Those models can be employed not only in astrophysics, but also in other areas of physical research and in optimization modeling of plasma-chemical and power facilities as well. The project results are intended for public and noncommercial use in the areas of basic and applied research, as well as for university educational programs. They will be published in leading physical and astronomical scientific journals, and will also be accessible through the Internet on the dedicated project Web-site.
Realization of the project completely follows the basic purposes and tasks of ISTC. The project is focused on the solution of the important scientific problem that has no military application but requires high level of expertise in various problems of high-energy-density physics achieved by the weapon specialists, both in the description of fundamental physical processes and in their numerical modeling. The solution of the project tasks will be achieved in close cooperation of the participants and foreign collaborators of the project carried out in the form of persistent interaction through the Internet, joint participation in the meetings, seminars and conferences. Scientific contacts with foreign collaborators also include direct exchange of theoretical and helioseismic data both obtained in the participating and collaborating institutions and selected from publications.
Institute of Physics, University of Rostock, Germany
Politecnico di Torino, Italy
University of South California, Department of Physics and Astronomy
University of Aarhus, Department of Physics and Astronomy