  We examine energy conversion from accreting pair plasma to outgoing Poynting
flux by black hole rotation. Our approach is based on a two-fluid model
consisting of collisionless pair plasma. The electric potential is not constant
along magnetic field lines, unlike an ideal magnetohydrodynamics approximation.
We show how and where longitudinal electric fields and toroidal magnetic fields
are generated by the rotation, whereas they vanish everywhere for radial flow
in a split monopole magnetic field in a Schwarzschild black hole. Outgoing
electromagnetic power in a steady state is calculated by applying the WKB
method to the perturbation equations for a small spin parameter. In our model,
the luminosity has a peak in the vicinity of the black hole, but is damped
toward the event horizon and infinity. The power at the peak is of the same
order as that in the Blandford--Znajek process, although the physical mechanism
is different.
