Stability of a self-gravitating homogeneous resistive plasma

PHYSICA D-NONLINEAR PHENOMENA

卷:241

Article

Pugliese, Daniela^1,2  Carlevaro, Nakia¹  Lattanzi, Massimiliano^1,3  Montani, Giovanni^1,4,5  Benini, Riccardo¹ 

[1] Univ Roma La Sapienza, Dipartimento Fis, I-00185 Rome, Italy

[2] Queen Mary Univ London, Sch Math Sci, London E1 4NS, England

[3] Oxford Astrophys, Oxford OX1 3RH, England

[4] UTFUS MAG, ENEA CR Frascati Rome, Rome, Italy

[5] INFN Sez, Milan, Italy

关键词: Plasma Physics;    Magnetohydrodynamics;    Jeans instability;   

DOI  :  10.1016/j.physd.2011.12.011

来源: Elsevier

【 摘 要 】

In this paper, we analyze the stability of a homogeneous self-gravitating plasma, having a non-zero resistivity. This study provides a generalization of the Jeans paradigm for determining the critical scale above which gravitational collapse is allowed. We start by discussing the stability of an ideal self-gravitating plasma embedded in a constant magnetic field. We outline the existence of an anisotropic feature of the gravitational collapse. In fact, while in the plane orthogonal to the magnetic field the Jeans length is enhanced by the contribution of the magnetic pressure, outside this plane perturbations are governed by the usual Jeans criterion. The anisotropic collapse of a density contrast is sketched in detail, suggesting that the linear evolution provides anisotropic initial conditions for the non-linear stage, where this effect could be strongly enforced. The same problem is then faced in the presence of non-zero resistivity and the conditions for the gravitational collapse are correspondingly extended. The relevant feature emerging in this resistive scenario is the cancelation of the collapse anisotropy in weakly conducting plasmas. In this case, the instability of a self-gravitating resistive plasma is characterized by the standard isotropic Jeans length in any directions. The limit of very small resistivity coefficient is finally addressed, elucidating how reminiscence of the collapse anisotropy can be found in the different values of the perturbation frequency inside and outside the plane orthogonal to the magnetic field. (C) 2011 Elsevier B.V. All rights reserved.

【 授权许可】

Free