2D Relativistic MHD simulations of the Kruskal–Schwarzschild instability in a relativistic striped wind

Abstract

We study the linear and non-linear development of the Kruskal-Schwarzchild Instability in a relativisitically expanding striped wind. This instability is the generalization of Rayleigh-Taylor instability in the presence of a magnetic field. It has been suggested to produce a selfsustained acceleration mechanism in strongly magnetized outflows found in active galactic nuclei, gamma-ray bursts, and micro-quasars. The instability leads to magnetic reconnection, but in contrast with steady-state Sweet-Parker reconnection, the dissipation rate is not limited by the current layer's small aspect ratio. We performed two-dimensional (2D) relativistic magnetohydrodynamic (RMHD) simulations featuring two cold and highly magnetized (1 σ 10 3 ) plasma layers with an anti-parallel magnetic field separated by a thin layer of relativistically hot plasma with a local effective gravity induced by the outflow's acceleration. Our simulations show how the heavier relativistically hot plasma in the reconnecting layer drips out and allows oppositely oriented magnetic field lines to reconnect. The instability's growth rate in the linear regime matches the predictions of linear stability analysis. We find turbulence rather than an ordered bulk flow near the reconnection region, with turbulent velocities up to ∼ 0.1c, largely independent of model parameters. However, the magnetic energy dissipation rate is found to be much slower, corresponding to an effective ordered bulk velocity inflow into the reconnection region v in = β in c, of 10 −3 β in 5 × 10 −3 . This occurs due to the slow evacuation of hot plasma from the current layer, largely because of the Kelvin-Helmholtz instability experienced by the dripping plasma. 3D RMHD simulations are needed to further investigate the non-linear regime.

Emission Mechanisms of Fast Radio Bursts

“…When the magnetic pulse arrives at the sheet, the sharp acceleration and compression cause violent reconnection. We can speculate that the current sheet is destroyed by the Kruskal-Schwarzschild instability [85,86], which is the magnetic counterpart of the Rayleigh-Taylor instability, so that the field line tubes with the oppositely directed fields fall into the magnetic pulse, forming multiple small current sheets scattered over the body of the pulse. Within each of the small current sheets, the reconnection process occurs via formation and merging of magnetic islands, which produces an fms noise.…”

Radiative signatures of plasmoid-dominated reconnection in blazar jets

“…Although the physical origin of theses blobs is unknown, a strong candidate is the magnetic reconnection process (Giannios et al 2009;Giannios 2013). Instabilities occurring in the blazar jet can result in the production of current sheets where the reconnection process is triggered (Spruit et al 2001;Giannios & Spruit 2006;Barniol Duran et al 2017;Gill et al 2018). These current sheets are susceptible to tearing instabilities which fragment the sheets into a chain of magnetic islands or plasmoids (Loureiro et al 2007;Uzdensky et al 2010;Fermo et al 2010;Huang & Bhattacharjee 2012;Loureiro et al 2012;Takamoto 2013), each containing relativistic particles and magnetic fields.…”

Fast radio bursts from reconnection in magnetar magnetosphere

“…When the magnetic pulse arrives at the sheet, the sharp acceleration and compression cause the violent reconnection. Moreover, the current sheet is destroyed by the Kruskal-Schwarzschild instability (Lyubarsky 2010;Gill et al 2018), which is the magnetic counterpart of the Rayleigh-Taylor instability, so that the field line tubes with the oppositely directed fields fall into the magnetic pulse forming multiple small current sheets scattered over the body of the pulse. Within each of the small current sheets, the reconnection process occurs via formation and merging of magnetic islands, which gives rise to an fms noise.…”