Abstract
An ubiquitous feature of stellar systems, particularly of transitional disks, is their variability across the full range of the electromagnetic spectrum. The contribution to the near-infrared region of the spectrum comes mainly from the inner region of the disk, where gas and dust are heated to extremely high temperatures. We present a new physical mechanism that can explain the near-infrared variability of some transitional disks. The main process is the intermittent formation of a sublimation wall due to an instability between the magnetic field of the star and the innermost disk region. When the wall is present, it contributes to the spectrum but also shadows part of the material beyond its location. Using this mechanism, we present a model to explain the near-infrared variability of the transitional disk around GM Aur.
