  The morphologies of planetary nebulae are believed to be self-organized
configurations. These configurations are modeled by three-dimensional
temporally self-similar magnetohydrodynamic solutions with radial flow, under
the gravitational field of a central star of mass $M$. These solutions
reproduce basic features, such as jets, point-symmetric knots, and filaments,
through plasma pressure, mass density, and magnetic field lines. The time
evolution function of the radial velocity starts as a slow wind and terminates
as a fast wind.
