Tidal torques on accretion discs in binary systems with extreme mass ratios

This paper investigates the tidal transport of angular momentum in accretion disc flow in a close binary system with small mass ratio, q. We demonstrate that the disc can only be tidally truncated if q is greater than the inverse of the Reynolds number. We derive the existence of a strong 2:1 resonance. Near the resonance, a spiral dissipation pattern is expected. If the Reynolds number is greater than ∼q−2, a dissipation and angular momentum loss from the disc may be sufficient to truncate it at the resonance. Finally we discuss the application of these results to dwarf novae.