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The physical mechanism of angular momentum transport in poorly ionizedregions of protoplanetary discs, the dead zones (DZs), is not understood. Thepresence of a DZ naturally leads to conditions susceptible to the Rossby waveinstability (RWI), which produces vortices and spiral density waves that mayrevive the DZ and be responsible for observed large-scale disc structures. Wepresent a series of two-dimensional hydrodynamic simulations to investigate therole of the RWI in DZs, including its impact on the long-term evolution of thedisc and its morphology. The nonlinear RWI can generate Reynolds stresses(effective $\alpha$ parameter) as large as $0.01 - 0.05$ in the DZ, helping tosustain quasi-steady accretion throughout the disc. It also produces novel discmorphologies, including azimuthal asymmetries with $m = 1, 2$, and atypicalvortex shapes. The angular momentum transport strength and morphology are mostsensitive to two parameters: the radial extent of the DZ and the discviscosity. The largest Reynolds stresses are produced when the radial extent ofthe DZ is less than its distance to the central star. Such narrow DZs lead to asingle vortex or two coherent antipodal vortices in the quasi-steady state. Theedges of wider DZs evolve separately, resulting in two independent vortices andreduced angular momentum transport efficiency. In either case, we find that,because of the Reynolds stresses generated by the nonlinear RWI, gravitationalinstability is unlikely to play a role in angular momentum transport across theDZ, unless the accretion rate is sufficiently high.

Rossby Wave Instability and Long-Term Evolution of Dead Zones in Protoplanetary Discs