Topic/Type: 1.1 Space & astrophysical plasmas, Poster

Decelerating magnetized relativistic two-component jets

Z. Meliani, R. Keppens

Centrum voor Plasma Astrofysica, KU Leuven, Belgium

Transverse stratification is a common intrinsic feature of astrophysical jets. There is growing evidence that jets in radio galaxies consist of a fast low density outflow at the jet
axis, surrounded by a slower, denser, extended jet. The inner and outer jet components then have a different origin and launching mechanism, making their magnetization, associated energy flux and
angular momentum content different as well. Their interface will develop differential rotation, where disruptions may occur. We here investigate the stability of magnetized, rotating, two-component relativistic outflows typical for jets in radio galaxies. For this purpose, we parametrically explore the long term evolution of radially stratified jets numerically, extending our previous study where a single, purely hydrodynamic evolution was considered. With grid-adaptive relativistic magnetohydrodynamic simulations, augmented with approximate linear stability analysis, we revisit the interaction between the two jet components. We study the influence of dynamically important magnetic fields, with varying contributions of the inner component jet to the total kinetic energy flux of the jet, on their non-linear azimuthal stability. We demonstrate that two-component jets with high kinetic energy flux, and an inner jet magnetization which is lower than the external jet magnetization are subject to the development of a relativistically enhanced, rotation-induced Rayleigh-Taylor type instability. This instability appears to play a major role in decelerating the inner jet and the overall jet decollimation. This novel deceleration scenario can partly explain the radio source dichotomy, relating it directly to the efficiency of the central engine in launching the inner jet component. The FRII/FRI transition could then occur when the relative kinetic energy flux of the inner to the external jet grows beyond a certain treshold.