A physical model for the flickering variability in cataclysmic variables
  Aperiodic broad-band variability (also known as flickering) is observed
throughout all types of accreting compact objects. Many statistical properties
of this variability can be naturally explained with the fluctuating accretion
disk model, where variations in the mass-transfer rate through the disk are
modulated on the local viscous timescale and propagate towards the central
compact object. Here, a recently developed implementation of the model is
applied for the first time to the time-averaged, high-frequency variability of
a cataclysmic variable star (MV Lyrae) observed with the Kepler satellite. A
qualitatively good fit to the data is achieved, suggesting the presence of
geometrically thick inner flow with large viscosity parameter, extending from
$\sim0.12R_{\odot}$ all the way to the white dwarf surface. A simple spectral
model of the system suggests that the geometrically thick component would not
contribute much to the observed optical flux originating from the geometrically
thin outer disk. Instead, X-ray reprocessing from the geometrically thick disk
onto the thin disk is proposed as a mechanism to explain the observed
variability. Similar flows are also deduced in accreting neutron stars/black
holes (X-ray binaries) and Active Galactic Nuclei. Additionally, eclipse
mapping studies of cataclysmic variables also seem to suggest the presence of a
geometrically extended flow towards the inner-edges of the accretion disk. The
fluctuating accretion disk model applied here is encouraging in understanding
the origin of flickering in cataclysmic variables, as well as in X-ray binaries
and Active Galactic Nuclei, by providing a unifying scheme by which to explain
the observed broad-band variability features observed throughout all compact
accreting systems.
