Description
"Protoplanetary disks are weakly ionized environments where the non-ideal MHD effects play an important role in the gas dynamics. As such, the magnetorotational instability (MRI) cannot operate everywhere and generate a fully turbulent disk. Instead, a so-called dead zone naturally occurs, where the turbulence level is low and dominated by non-MRI stresses (e.g. hydrodynamic instabilities). The most promising location of a dead zone is its outer edge. Previous studies have shown that the dead zone outer edge can efficiently trap dust particles, hence being a possible explanation for the origin of the observed disk sub-structures. In order to properly assess the dead zone mechanism as a potential candidate, gas/dust evolution and non-ideal MHD calculations must be coupled. The first step towards this goal is to obtain an appropriate parameter encoding the disk turbulence level called the
turbulent parameter alpha. In this talk, I will present a 1+1D magnetically-driven disk accretion model that self-consistently determine the turbulent alpha-parameter from detailed considerations of the MRI and non-ideal MHD effects (Ohmic resistivity and Ambipolar diffusion) -given stellar properties (mass and luminosity), disk mass and dust properties. The main processes we include are: (1) irradiation from the forming star; (2) dust settling; (3) ionization from stellar X-rays, galactic cosmic rays and the decay of short/long-lived radionuclides; (4) disk chemistry; (5) turbulence driven by the MRI accretion and hydrodynamics instabilities. Particularly, we apply our framework to investigate the outer structure of steady-state viscously accreting protoplanetary disks, and determine what are the key parameters at play by conducting an exhaustive parameter study."
