  We obtained high temporal resolution spectroscopy of the unusual binary
system AR Sco covering nearly an orbit. The H$\alpha$ emission shows a complex
line structure similar to that seen in some polars during quiescence. Such
emission is thought to be due to long-lived prominences originating on the red
dwarf. A difference between AR Sco and these other systems is that the white
dwarf in AR Sco is rapidly spinning relative to the orbital period. "Slingshot"
prominences stable at 3 to 5 stellar radii require surface magnetic fields
between 100 and 500 G. This is comparable to the estimated WD magnetic field
strength near the surface of the secondary. Our time-resolved spectra also show
emission fluxes, line equivalent widths, and continuum color varying over the
orbit and the beat/spin periods of the system. During much of the orbit, the
optical spectral variations are consistent with synchrotron emission with the
highest energy electrons cooling between pulses. On the time-scale of the
beat/spin period we detect red and blue-shifted H$\alpha$ emission flashes that
reach velocities of 700 km/s. Red-shifted Balmer emission flashes are
correlated with the bright phases of the continuum beat pulses while
blue-shifted flashes appear to prefer the time of minimum in the beat light
curve. We propose that much of the energy generated in AR Sco comes from fast
magnetic reconnection events occurring near the inward face of the secondary
and we show that the energy generated by magnetic reconnection can account for
the observed excess luminosity from the system.
