Recent observations revealed that many kinds of astrophysical outflows have very similar structure, i.e. bipolar jets are surrounded by an equatorial (disk-shaped) wind or an expanded wind as in the outflows from YSO's, post AGB stars, pulsars or AGN's. One might think that this is very queer because the species of the central objects and the spatial scales are quite different among these objects. However this similarity is a result of self-organized magnetospheric equilibrium. In these systems, the rotating magnetic field plays an important role for the structure formation. In such systems, two components of the Lorentz force (the electrostatic force and the magnetic force arising from the toroidal component) dominate other forces in the region far distant from the rotation axis in spite of the difference of the acceleration mechanism of the flows. We can understand that such similarity of the structures is a nature of the plasma outflows itself.

We suppose relativistic, pressure-free, inviscid, resistive-less, stationary and axisymmetric MHD flows. In this case, MHD equations reduce to well known basic equations: the Bernoulli equation and the Grad-Shafranov equation. We should note that the special relativistic treatment is necessary to discuss the structure far beyond the light cylinder, even if the flow speed is not close to the light velocity.