A possible manifestation of spiral shock waves in the accretion disks of cataclysmic variables

We present the results of three-dimensional numerical simulations of flow s tructures in binary systems with spiral shock waves. Variations of the mass -transfer rate perturb the equilibrium state of the accretion disk; consequ ently, a condensation (blob) behind the shock breaks away from the shock fr ont and moves through the disk with variable speed. Our computations indica te that the blob is a long-lived formation, whose mean parameters do not va ry substantially on timescales of several tens of orbital periods of the sy stem. The presence of the spiral shocks maintains the compact blob in the d isk: it prevents the blob from spreading due to the differential motion of matter in the disk, and dissipative spreading on this timescale is negligib le. A number of cataclysmic variables display periodic or quasi-periodic ph otometric variations in their light curves with characteristic periods simi lar to0.1-0.2P(orb), where P-orb is the orbital period. The blobs formed in systems with spiral shock waves are examined as a possible origin for thes e variations. The qualitative (and, in part, quantitative) agreement betwee n our computations and observations of IP Peg and EX Dra provides evidence for the efficacy of the proposed model. (C) 2001 MAIK "Nauka/Interperiodica ".