  Recently, Beloborodov suggested that there exists a resonance phenomenon
between an extremely intense electromagnetic wave and internal magnetized
particles. The particles exchange energy with the wave at frequent resonance
events and then reach the radiation reaction limit immediately. This process
greatly enhances the scattering cross section of the particles. Note that these
results only involve an extraordinary (X) mode wave. In this paper, we focus on
an intense ordinary (O) mode wave propagating through magnetized particles and
compare it with the case of the X-mode wave. Our result shows that the
scattering cross section of the particles in the O-mode wave is significantly
smaller than that in the X-mode wave. This has important implications for the
transparency of a fast radio burst (FRB) inside the magnetosphere of a
magnetar. We argue that there is a strong scattering region in the stellar
magnetosphere, within which an O-mode wave is more transparent than an X-mode
wave for an FRB.
