A wide range of stars has significant magnetic fields. They typically represent either very early stages of stellar evolution (so-called T Tauri stars), which carry important information about the formation of stars and protoplanetary disks, or end stages of evolution (white dwarfs, neutron stars), which consist of exotic matter and carry information about the evolutionary paths of stars in our Galaxy. The observable properties of these stars strongly depend on the accretion rate of material to their surface, on the pattern of matter flow in the magnetospheres around them, and on the interaction of magnetic field lines with the surrounding matter. Observations, however, are not sufficient to understand the processes in these systems because the spatial details remain unresolved. Nor can the problem of disk or wind accretion to a magnetized star be solved analytically. Thorough two- and three-dimensional simulations are necessary to understand the physics of plasma flow around magnetized stars. In this project the investigators are concentrating mainly on three dimensional simulations of several problems which are important for the understanding of the observations. These include simulations of disk accretion to a star with a dipole magnetic field at different inclination angles of the magnetic pole, different rotation rates of the star, different mass accretion rates, and simulations of accretion directly to a strongly or weakly magnetized star. The simulations will supply the necessary models to interpret observations of different astronomical objects.
Broader impact: This research continues to attract many undergraduate and graduate students. Training students is considered an important part of the overall project. Typically, four to six undergraduate students work on different parts of the project, and one to two graduate students work on longer-term projects gaining experience with scientific research. They learn magnetohydrodynamics and programming, perform simulation runs with different parameters, and learn how to analyze data using different tools including visualization and animation. The developed methods and numerical codes also have general value and are applicable in other areas of science: planetary science, geophysics, magnetosphere science, solar science, and in engineering.
