Spatial aspect of wave transformations in astrophysical flows

¹ Osservatorio Astronomico di Torino, Strada dell'Osservatorio 20, 10025 Pino Torinese, Italy
² Centre for Plasma Astrophysics, K.U. Leuven, Celestijnenlaan 200B, 3001 Heverlee, Belgium
³ Dipartimento di Fisica Generale, Universitá degli Studi di Torino, Via Pietro Giuria 1, 10125 Torino, Italy
⁴ Abdus Salam International Centre for Theoretical Physics, 34014 Trieste, Italy

Corresponding author: G. Bodo, bodo@to.astro.it

Received: 28 March 2001
Accepted: 17 May 2001

Abstract

The phenomenon of Shear Induced wave Transformations (SITs) (Chagelishvili et al. 1996), is a common feature of flows, sustaining mode of wave motion. Until now this "nonmodal" phenomenon was described only in terms of the time evolution of individual Fourier harmonics of perturbations in the space of wave numbers (k-space). In this paper we present the results of the first, direct numerical simulations of SITs, giving compelling evidence in favor of the robust and recognizable character of SITs. The importance of these results for an understanding of physical processes in astrophysical shear flows is pointed out. Namely, concrete astrophysical situations (solar plasma flows, galactic gaseous disks, accretion disks and accretion-ejection flows), where this approach may help to shed some light on observational appearances of related objects, are indicated and discussed.