  One of the early hypotheses about the origin of FUOR outbursts explains them
by the fall of gas clumps from the remnants of protostellar clouds onto
protoplanetary disks surrounding young stars (Hartmann and Kenyon 1985). To
calculate the consequences of such an event we make 3D hydrodynamic simulations
by SPH method. It is shown that the fall of the clump on the disk in the
vicinity of the star actually causes a burst of the star's accretion activity,
resembling in its characteristics the flares of known FUORs. In the region of
incidence, an inhomogeneous gas ring is formed, which is inclined relative to
the outer disk. During several revolutions around the star, this ring combines
with the inner disk and forms a tilted disk. In the process of evolution, the
inner disk expands, and its inclination relative to the outer disk decreases.
After 100 revolutions, the angle of inclination is a few degrees. This result
is of interest in connection with the discovery in recent years of
protoplanetary disks, the inner region of which is inclined relative to the
outer one. Such structures are usually associated with the existence in the
vicinity of a star of a massive body (planet or brown dwarf), whose orbit is
inclined relative to the plane of the disk. The results of our modeling
indicate the possibility of an alternative explanation for this phenomenon.

Solar and Stellar Astrophysics