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Register a new userRelativistic magnetohydrodynamical simulations of the resonant corrugation of a fast shock front
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Camilia Demidem
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The generation of turbulence at magnetized shocks and its subsequent interaction with the latter is a key question of plasma- and high-energy astrophysics. This paper presents two-dimensional magnetohydrodynamic simulations of a fast shock front interacting with incoming upstream perturbations, described as harmonic entropy or fast magnetosonic waves, both in the relativistic and the sub-relativistic regimes. We discuss how the disturbances are transmitted into downstream turbulence and we compare the observed response for small amplitude waves to a recent linear calculation. In particular, we demonstrate the existence of a resonant response of the corrugation amplitude when the group velocity of the outgoing downstream fast mode matches the velocity of the shock front. We also present simulations of large amplitude waves to probe the non-linear regime.
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As a shock front interacts with turbulence, it develops corrugation which induces outgoing wave modes in the downstream plasma. For a fast shock wave, the incoming wave modes can either be fast magnetosonic waves originating from downstream, outrunning the shock, or eigenmodes of the upstream plasma drifting through the shock. Using linear perturbation theory in relativistic MHD, this paper provides a general analysis of the corrugation of relativistic magnetized fast shock waves resulting from their interaction with small amplitude disturbances. Transfer functions characterizing the linear response for each of the outgoing modes are calculated as a function of the magnetization of the upstream medium and as a function of the nature of the incoming wave. Interestingly, if the latter is an eigenmode of the upstream plasma, we find that there exists a resonance at which the (linear) response of the shock becomes large or even diverges. This result may have profound consequences on the phenomenology of astrophysical relativistic magnetized shock waves.
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