Aspect ratio dependence in magnetorotational instability shearing box simulations

¹ INAF, Osservatorio Astronomico di Torino, Strada Osservatorio 20, Pino Torinese, Italy e-mail: bodo@to.astro.it
² Dipartimento di Fisica Generale, Universitá di Torino, via Pietro Giuria 1, 10125 Torino, Italy
³ Department of Astronomy and Astrophysics, The University of Chicago, 5640 S. Ellis ave., Chicago IL 60637, USA

Received: 6 March 2008
Accepted: 9 May 2008

Abstract

Aims. We study the changes in the properties of turbulence driven by the magnetorotational instability in a shearing box, as the computational domain size in the radial direction is varied relative to the height.

Methods. We perform 3D simulations in the shearing box approximation, with a net magnetic flux, and we consider computational domains with different aspect ratios.

Results. We find that in boxes of aspect ratio unity the transport of angular momentum is strongly intermittent and dominated by channel solutions in agreement with previous work. In contrast, in boxes with larger aspect ratios, the channel solutions and the associated intermittent behavior disappear.

Conclusions. There is strong evidence that, as the aspect ratio becomes larger, the characteristics of the solution become aspect ratio independent. We conclude that shearing box calculations with an aspect ratio of unity or near unity may introduce spurious effects.