Spiral density wave generation by vortices in Keplerian flows

¹ INAF Osservatorio Astronomico di Torino, Strada dell'Osservatorio 20, 10025 Pino Torinese, Italy e-mail: bodo@to.astro.it
² Center for Plasma Astrophysics, Abastumani Astrophysical Observatory, 2a Kazbegi Ave., Tbilisi 0160, Georgia
³ Dipartimento di Fisica Generale dell'Università, via Pietro Giuria 1, 10125 Torino, Italy

Received: 7 April 2004
Accepted: 28 February 2005

Abstract

We perform a detailed analytical and numerical study of the dynamics of perturbations (vortex/aperiodic mode, Rossby and spiral-density waves) in 2D compressible disks with a Keplerian law of rotation. We draw attention to the process of spiral-density wave generation from vortices, discussing, in particular, the initial, most peculiar stages of wave emission. We show that the linear phenomenon of wave generation by vortices in smooth (without inflection points) shear flows found by using the so-called non-modal approach, is directly applicable to the present case. After an analytical non-modal description of the physics and characteristics of the spiral-density wave generation/propagation in the local shearing-sheet model, we follow the process of wave generation by small amplitude coherent circular vortex structures, by direct global numerical simulation, describing the main features of the generated waves.