2. The vertical structure
We assume that
The equation for hydrostatic equilibrium in the vertical direction is
where P, T, and µ are the gas pressure, temperature, density and molecular weight respectively and z the vertical coordinate, is the gravitational component in the z direction. The extinction coefficient is given by where and are the volume absorption and scattering coefficients respectively. The total radiative flux is F.
The condition of thermal equilibrium is:
where is the viscous energy dissipation per unit volume.
We assume here that the entire energy dissipated by the viscous forces is carried away by radiation i.e. we ignore at this moment convection and any other non radiative energy transport mechanisms. The radiative transfer equation is:
where in the notation of SW and we use the model approximation for the viscous energy dissipation.
The boundary conditions are:
The above equations, together with the boundary conditions form a closed set, and can be solved for the disc structure for given and .
© European Southern Observatory (ESO) 1999
Online publication: March 18, 1999