  AR~Scorpii is an intermediate polar system composed of a magnetic white dwarf
(WD) and an M-type star, and shows non-thermal, pulsed, and highly linearly
polarized emission. The radio/optical emission modulates with the WD's spin and
show the double peak structure in the light curves. In this paper, we discuss a
possible scenario for the radiation mechanism of AR~Scorpii. The magnetic
interaction on the surface of the companion star produces an outflow from the
companion star, the heating of the companion star surface, and the acceleration
of electrons to a relativistic energy. The accelerated electrons, whose typical
Lorentz factor is $\sim 50-100$, from the companion star move along the
magnetic field lines toward the WD surface. The electrons injected with the
pitch angle of $\sin\theta_{p,0}>0.05$ are subject to the magnetic mirror
effect and are trapped in the closed magnetic field line region.We find that
the emission from the first magnetic mirror points mainly contributes to the
observed pulsed emission and the formation of the double-peak structure in the
light curve. For the inclined rotator, the pulse peak in the calculated light
curve shifts the position in the spin phase, and a Fourier analysis exhibits a
beat frequency feature, which are consistent with the optical/UV observations.
The pulse profile also evolves with the orbital phase owing to the effect of
the viewing geometry. The model also interprets the global features of the
observed spectral energy distribution in radio to X-ray energy bands. We also
discuss the curvature radiation and the inverse-Compton scattering process in
the outer gap accelerator of the WD in AR Scorpii and discuss the possibility
of the detection by future high-energy missions.
