  Apart from regular, low-level stochastic variability, some AGN occasionally
show exceptionally large changes in the luminosity, spectral shape, and/or
X-ray absorption. The most notable are the changes of the spectral type when
the source classified as a Seyfert 1 becomes a Seyfert 2 galaxy or vice versa.
Thus a name was coined of 'Changing-Look AGN' (CL AGN). The origin of this
phenomenon is still unknown, but for most of the sources, there are strong
arguments in favor of the intrinsic changes. Understanding the nature of such
rapid changes is a challenge to the models of black hole accretion flows since
the timescales of the changes are much shorter than the standard disk viscous
timescales. We aim to model the CL AGN phenomenon assuming that the underlying
mechanism is the time-dependent evolution of a black hole accretion disk
unstable due to the dominant radiation pressure. We use a 1-dimensional,
vertically integrated disk model, but we allow for the presence of the hot
coronal layer above the disk and the presence of the inner purely hot flow. We
focus on the variability timescales and amplitudes, which can be regulated by
the action of large-scale magnetic fields, the description of the disk-corona
coupling, and the presence of an inner optically thin flow, like
Advection-Dominated Accretion Flow (ADAF). We compare model predictions for the
accretion disk around black hole mass 10$^7$M$_{\odot}$.
