Inhomogeneous magnetic seed fields and gravitational waves within the magnetohydrodynamic limit
- Astrophysics, University of Oxford, Denys Wilkinson Building, Keble Road, Oxford OX1 3RH (United Kingdom)
- Department of Mathematics and Applied Mathematics, University of Cape Town, 7701 Rondebosch (South Africa)
- Department of Physics, Umeaa University, SE-901 87 Umeaa (Sweden)
In this paper we apply second-order gauge-invariant perturbation theory to investigate the possibility that the coupling between gravitational waves (GWs) and a large-scale inhomogeneous magnetic field acts as an amplification mechanism in an 'almost' Friedmann-Lemaitre-Robertson-Walker Universe. The spatial inhomogeneities in the magnetic field are consistently implemented using the magnetohydrodynamic (MHD) approximation, which yields an additional source term due to the interaction of the magnetic field with velocity perturbations in the plasma. Comparing the solutions with the corresponding results in our previous work indicates that, on superhorizon scales, the interaction with the spatially inhomogeneous field in the dust regime induces the same boost as the case of a homogeneous field, at least in the ideal MHD approximation. This is attributed to the observation that the MHD induced part of the generated field effectively only contributes on scales where the coherence length of the initial field is less than the Hubble scale. At subhorizon scales, the GW induced magnetic field is completely negligible in relation to the MHD induced field. Moreover, there is no amplification found in the long-wavelength limit.
- OSTI ID:
- 20774673
- Journal Information:
- Physical Review. D, Particles Fields, Vol. 73, Issue 10; Other Information: DOI: 10.1103/PhysRevD.73.103509; (c) 2006 The American Physical Society; Country of input: International Atomic Energy Agency (IAEA); ISSN 0556-2821
- Country of Publication:
- United States
- Language:
- English
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