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| Author(s): |
Natalia Fernanda de Souza Andrade
Total Authors: 1
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| Document type: | Master's Dissertation |
| Press: | São Paulo. |
| Institution: | Universidade de São Paulo (USP). Instituto Astronômico e Geofísico (IAG/SBD) |
| Defense date: | 2020-02-28 |
| Examining board members: |
Vera Jatenco Silva Pereira;
Alex Cavalieri Carciofi;
Diego Antonio Falceta Gonçalves;
Annibal Hetem Junior
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| Advisor: | Vera Jatenco Silva Pereira |
| Abstract | |
Accretion disks are commonly observed around young stars, such as T Tauri stars. In order for the accretion to happen, the disk particles must lose their rotational energy and fall towards the central object. The most promising mechanism for angular momentum transport in accretion disks is the Magnetorotational Instability (MRI). This instability, however, requires that the gas particles be coupled to the magnetic field lines. Thus, a fraction of the particles must be charged. As the disk temperatures are too low, the particles exhibit a low ionization fraction. Therefore, to assure the occurrence of the MRI in the whole disk, higher temperatures are required. Many works in the literature have proposed the damping of Alfvén waves as an extra energy source in disks. The considered mechanisms were: the nonlinear damping and the turbulent damping. In this work, we have studied, in 2D, the nonlinear and turbulent dampings and introduce a new mechanism, not yet applied to this environment, the resonant absorption of surface Alfvén waves, and analyse how each of these mechanisms can heat the disk. We also propose that the resonant absorption can be coupled to the turbulent damping, through the Kelvin-Helmholtz Instability. Our results show that, since the resonant absorption does not provoke any expressive heating in the disk, changes in the disk structure associated with this mechanism are inexistent, while the nonlinear damping is significant only for very high Alfvén wave fluxes. The coupled mechanism, on the other hand, despite significantly heat the disk, being more effective than the nonlinear and resonant mechanisms in most cases, generates smaller temperatures than the turbulent damping, the most effective mechanism among those considered in this work. (AU) | |
| FAPESP's process: | 17/26042-2 - Heating mechanisms of protostellar accretion disks |
| Grantee: | Natália Fernanda de Souza Andrade |
| Support Opportunities: | Scholarships in Brazil - Master |