The Accretion disk in AGNs is a multi-temperature/multi-phase structure that funnels material from large scales, through the innermost flow, onto the black hole. This thematic area addresses the following key questions:

— Which insights can variability offer on the structure and physical conditions of accretion disks? What is its distance and causal relation to other emitting structures, e.g. broad-line region?

— How does the disk variability relate to the fundamental properties of the system such black hole mass spin, accretion rate?

— Can we use our understanding of the optical/UV variability of type I and type II AGNs to test the Unification hypothesis or identify variability outliers and peculiar signals (e.g. extreme variability events or periodic oscillations) that expand the parameter space of accretion flow studies?

The special focus of the “Accretion disk” thematic area is to obtain a comprehensive characterisation of AGN lightcurves using current and upcoming data-avalanche missions (e.g. VST, GAIA, CRTS, ZTF, and ultimately the Vera Rubin’s Legacy Survey of Space & Time – LSST) through high cadence monitoring over decadal timescales in half the sky, as well as the development of the state-of-the-art machine learning algorithms and novel phenomenological models of multi-phase accretion flows.