  We investigate in details properties of stationary force-free magnetosphere
of aligned rotator assuming the last closed field line lying in equatorial
plane at large distances from pulsar. The pulsar equations is solved
numerically using multigrid code with high numerical resolution, physical
properties of the magnetosphere are obtained with high accuracy. We found a set
of solutions with different sizes of the closed magnetic field line zone and
verify the applicability of the force-free approximation. We discuss the role
of electron-positron cascades in supporting of the force-free magnetosphere and
argue that the closed field line zone should grow with time slower than the
light cylinder. This yield the pulsar breaking index less than 3. It is shown,
that models of aligned rotator magnetosphere with widely accepted configuration
of magnetic field, like one considered in this paper, have serious
difficulties. We discuss solutions of this problem and argue that in any case
pulsar energy losses should evolve with time differently than predicted by the
magnetodipolar formula.
