  This paper is concerned with an initial and boundary value problem of the
one-dimensional planar MHD equations for viscous, heat-conducting,
compressible, ideal polytropic fluids with constant transport coefficients and
large data. The vanishing shear viscosity limit is justified and the
convergence rates are obtained. More important, to capture the behavior of the
solutions at vanishing shear viscosity, both the boundary-layer thickness and
the boundary-layer solution are discussed. As by-products, the global
well-posedness of strong solutions with large data is established. The proofs
are based on the global (uniform) estimates which are achieved by making a full
use of the "effective viscous flux", the material derivatives and the structure
of the one-dimensional equations.
