Supervisors info:
Βλαχάκης Νεκτάριος, Αναπληρωτής Καθηγητής, τμήμα Φυσικής, Εθνικό και Καποδιστριακό Πανεπιστήμιο Αθηνών
Summary:
Accretion disks play an important role in contemporary astrophysics, as they are one of the most efficient ways to release gravitational energy into the universe. They are directly related to many energetic phenomena, such as astrophysical jets and magnetized winds. They have been observed directly or indirectly in a variety of astrophysical objects such as Young Stellar Objects, binary systems (Microquasars, X-ray binaries, cataclysmic variables), active galactic nuclei (Active Galactic Nuclei) and Gamma Ray Bursts.
In the present master thesis we study the dynamics inside a magnetized accretion disk, using the theory of non-ideal magnetohydrodynamics (resistive MHD), which includes the effects of magnetic field diffusion and viscosity. Using the assumptions of axisymmetry and steady state, as well as the symmetry of self-similarity, the system of partial differential equations is transformed into a system of ordinary differential equations, which can be treated numerically. The choice of the appropriate energy equation is discussed. Then these equations are written in non-dimensional units and in the appropriate way for numerical integration. Also, the critical points of the equations are identified and we discuss the way we can treat them.
Through the integration of these equations, we present solutions inside the disk for all physical quantities and for different types of disks, depending on the levels of magnetic field diffusion and viscosity. Based on these results, the physical processes that take place inside the disk are discussed, such as the mechanism of matter outflow and the loss of angular momentum. Finally, we discuss how one should approach the full problem, including sources of heating (Joule and Viscous heating) in the energy equation.
Keywords:
Magnetohydrodynamics, ideal, non-ideal, MHD, Accretion Disks, Jets
