  We report the analysis result of UV/X-ray emission from AR~Scorpii, which is
an intermediate polar (IP) composed of a magnetic white dwarf and a M-type
star, with the XMM-Newton data. The X-ray/UV emission clearly shows a large
variation over the orbit, and their intensity maximum (or minimum) is located
at the superior conjunction (or inferior conjunction) of the M-type star orbit.
The hardness ratio of the X-ray emission shows a small variation over the
orbital phase, and shows no indication of the absorption by an accretion
column. These properties are naturally explained by the emission from the
M-type star surface rather than from the accretion column on the WD's star
similar to the usual IPs. Beside, the observed X-ray emission also modulates
with WD's spin with a pulse fraction of $\sim 14\%$. The peak position is
aligned in the optical/UV/X-ray band. This supports the hypothesis that the
electrons in AR~Scorpii are accelerated to a relativistic speed, and emit
non-thermal photons via the synchrotron radiation. In the X-ray bands, the
evidence of the power-law spectrum is found in the pulsed component, although
the observed emission is dominated by the optically thin thermal plasma
emissions with several different temperatures. It is considered that the
magnetic dissipation/reconnection process on the M-type star surface heats up
the plasma to a temperature of several keV, and also accelerates the electrons
to the relativistic speed. The relativistic electrons are trapped in the WD's
closed magnetic field lines by the magnetic mirror effect. In this model, the
observed pulsed component is explained by the emissions from the first magnetic
mirror point.
