  Blazars show variability on timescales ranging from minutes to years, the
former being comparable to and in some cases even shorter than the
light-crossing time of the central black hole. The observed gamma-ray
lightcurves can be described by a power-law power density spectrum (PDS), with
a similar index for both BL Lacs and flat-spectrum radio quasars. We show that
this variability can be produced by turbulence in relativistic jets launched by
magnetically arrested accretion flows (MADs). We perform radiative transport
calculations on the turbulent, highly-magnetized jet launching region of a MAD
with a rapidly rotating supermassive black hole. The resulting synchrotron and
synchrotron self-Compton emission, originating from close to the black hole
horizon, is highly variable. This variability is characterized by PDS which is
remarkably similar to the observed power-law spectrum at frequencies less than
a few per day. Furthermore, turbulence in the jet launching region naturally
produces fluctuations in the plasma on scales much smaller than the horizon
radius. We speculate that similar turbulent processes, operating in the jet at
large radii (and therefore high bulk Lorentz factor), are responsible for
blazar variability over many decades in frequency, including on minute
timescales.
