  It has recently been demonstrated that self-consistent particle-in-cell
simulations of low-obliquity pulsar magnetospheres in flat spacetime show weak
particle acceleration and no pair production near the poles. We investigate the
validity of this conclusion in a more realistic spacetime geometry via
general-relativistic particle-in-cell simulations of the aligned pulsar
magnetospheres with pair formation. We find that the addition of frame-dragging
effect makes local current density along the magnetic field larger than the
Goldreich-Julian value, which leads to unscreened parallel electric fields and
the ignition of a pair cascade. When pair production is active, we observe
field oscillations in the open field bundle which could be related to pulsar
radio emission. We conclude that general relativistic effects are essential for
the existence of pulsar mechanism in low obliquity rotators.
