  Structures of X-ray emitting magnetic polar regions on neutron stars in X-ray
pulsars are studied in a range of the accretion rate, 10$^{17}$ g s$^{-1} \sim
10^{18}$ g s$^{-1}$. It is shown that a thin but tall, radiation energy
dominated, X-ray emitting polar cone appears at each of the polar regions. The
height of the polar cone is several times as large as the neutron star radius.
The energy gain due to the gravity of the neutron star in the polar cone
exceeds the energy loss due to photon diffusion in the azimuthal direction of
the cone, and a significant amount of energy is advected to the neutron star
surface. Then, the radiation energy carried with the flow should become so
large for the radiation pressure to overcome the magnetic pressure at the
bottom of the cone. As a result, the matter should expand in the tangential
direction along the neutron star surface, dragging the magnetic lines of force,
and form a mound-like structure. The advected energy to the bottom of the cone
should finally be radiated away from the surface of the polar mound and the
matter should be settled on the neutron star surface there. From such
configurations, we can expect an X-ray spectrum composed of a multi-color
blackbody spectrum from the polar cone region and a quasi-single blackbody
spectrum from the polar mound region. These spectral properties agree with
observations. A combination of a fairly sharp pencil beam and a broad fan beam
is expected from the polar cone region, while a broad pencil beam is expected
from the polar mound region. With these X-ray beam properties, basic patterns
of pulse profiles of X-ray pulsars can be explained too.
