out the accelerating electric field above the so-called pair formation front (PFF). It is generally believed that the observed radio emission is basically coming from upper part of the PC region. The SG, which is the rim of the PC, extends along the last-open-field line. There is no sufficient acceleration to emit gamma-rays producing electron-positron pairs at the low altitude because the field-aligned electric field near the last open field line is weak. Therefore, particle acceleration lasts up to high altitudes of many stellar radii. For this reason, the SG can provide extended high-energy emission above the last-open-field lines. The OG is located between a neighborhood of the null charge surface and the light cylinder along the open field lines. The accelerating electric field exists because of charge depletion, and photon-photon pair production occurs in the gap. The OG can also provide extended high energy emission. In addition, SG and OG models have roughly simple exponential spectral cutoff, which is more gradual than that of PC models.

SG and/or OG models can explain the double-peaked gamma-ray light curves (eg, [@b7; @b8]). On the other hand, PC models have much more difficulty reproducing the observed wide pulse profile because the beam 