2025MNRAS.537.2695C

Late-stage infall onto evolved protoplanetary discs is an important source of material and angular momentum replenishment and disc substructures. In this paper, we used 3D smoothed particle hydrodynamics simulations to model streamer-disc interactions for a prograde streamer. The initially parabolic streamer interacts with the disc material to excite disc eccentricity, which can last on the order of $10^5$ yr. We found that the spiral arms the streamer excited in the disc can have a variety of pattern speeds, ranging from stationary to super-Keplerian. Spiral arms with various pattern speeds can exist simultaneously, providing a way to diagnose them in observations. Streamer-induced spirals appear similar to those generated by a massive outer companion, where the pitch angle of the spiral increases towards the source of the perturbation. Additionally, the spiral arms can show large and sudden pitch angle changes. Streamer-induced spirals are long-lived, lasting approximately $3\!-\!4$ times longer than the initial streamer infall time-scale (${\sim} 10^4$ yr). After the initial interaction with the disc, a long-lasting low m azimuthal mode persists in the disc.