Anisotropic convection in rotating proto-neutron stars

¹ Departament de Física Aplicada, Universitat d'Alacant, Ap. Correus 99, 03080 Alacant, Spain
² A. F. Ioffe Institute of Physics and Technology and Isaak Newton Institute of Chili, Branch in St. Petersburg, 194021 St. Petersburg, Russia

Corresponding author: J. A. Pons, Jose.A.Pons@uv.es

Received: 11 December 2003
Accepted: 17 February 2004

Abstract

We study the conditions for convective instability in rotating, non-magnetic proto-neutron stars. The criteria that determine stability of nascent neutron stars are analogous to the Solberg-Høiland conditions but including the presence of lepton gradients. Our results show that, for standard angular velocity profiles, convectively unstable modes with wave-vectors parallel to the rotation axis are suppressed by a stable angular momentum profile, while unstable modes with wave-vectors perpendicular to the axis remain unaltered. Since the wave-vector is perpendicular to the velocity perturbation, the directional selection of the unstable modes may result in fluid motions along the direction of the rotation axis. This occurs in rigidly rotating stars as well as in the inner core of differentially rotating stars. Our results provide a natural source of asymmetry for proto-neutron stars with the only requirement that angular velocities be of the order of the convective characteristic frequency.