SIMBAD references

The origin and strength of the magnetic field in some systems like active galactic nuclei or gamma-ray bursts is still an open question in astrophysics. A possible mechanism to explain the magnetic field amplification is the Kelvin-Helmholtz instability, since it is able to transform the kinetic energy in a shear flow into magnetic energy. Through this work, we investigate the linear and non-linear effects produced by the magnetic susceptibility in the development of the Kelvin-Helmholtz instability in a relativistic plasma. The system under study consists of a plane interface separating two uniform fluids that move with opposite velocities. The magnetic field in the system is parallel to the flows and the susceptibility is assumed to be homogeneous, constant in time, and equal in both fluids. In particular, we analyse the instability in three different cases, when the fluids are diamagnetic, paramagnetic, and when the susceptibility is zero. We compute the dispersion relation in the linear regime and found that the interface between diamagnetic fluids is more stable than between paramagnetic ones. We check the analytical results with numerical simulations, and explore the effect of the magnetic polarization in the non-linear regime. We find that the magnetic field is more amplified in paramagnetic fluids than in diamagnetic ones. Surprisingly, the effect of the susceptibility in the amplification is stronger when the magnetization parameter is smaller. The results of our work make this instability a more efficient and effective amplification mechanism of seed magnetic fields when considering the susceptibility of matter.