Search results for "Lorentz factor"
showing 10 items of 38 documents
Numerical Relativistic Hydrodynamics
2008
High Resolution Shock Capturing (HRSC) techniques achieve highly accurate numerical approximations (formally second order or better) in smooth regions of the flow, and capture the motion of unresolved steep gradients without creating spurious oscillations. I will show how these techniques have been extended to relativistic hydrodynamics, making it possible to explore some challenging astrophysical scenarios. I will review recent literature concerning the main properties of different special relativistic Riemann solvers, and discuss several test problems which are commonly used to evaluate the performance of numerical methods in relativistic hydrodynamics. In the second part, I will illustra…
Morphology and Dynamics of Relativistic Jets
1997
We present a comprehensive analysis of the morphology and dynamics of relativistic pressure-matched axisymmetric jets. The numerical simulations have been carried out with a high-resolution shock-capturing hydrocode based on an approximate relativistic Riemann solver derived from the spectral decomposition of the Jacobian matrices of relativistic hydrodynamics. We discuss the dependence of the jet morphology on several parameters, paying special attention to the relativistic effects caused by high Lorentz factors and large internal energies of the beam flow. The parameter space of our analysis is spanned by the ratio of the beam and ambient medium rest mass density (η), the beam Mach number…
3D Relativistic Hydrodynamics
2007
We review the evolution of the numerical techniques applied in relativistic hydrodynamics since the sixties until today. We focus our attention on the state-of- the-art high-resolution shock-capturing methods and the astrophysical applications involving three-dimensional simulations.
Numerical simulations of the internal shock model in magnetized relativistic jets of blazars
2015
The internal shocks scenario in relativistic jets is used to explain the variability of the blazar emission. Recent studies have shown that the magnetic field significantly alters the shell collision dynamics, producing a variety of spectral energy distributions and light-curves patterns. However, the role played by magnetization in such emission processes is still not entirely understood. In this work we numerically solve the magnetohydodynamic evolution of the magnetized shells collision, and determine the influence of the magnetization on the observed radiation. Our procedure consists in systematically varying the shell Lorentz factor, relative velocity, and viewing angle. The calculatio…
Orbital evolution of colliding star and pulsar winds in 2D and 3D; effects of: dimensionality, EoS, resolution, and grid size
2015
(abridged)The structure formed by the shocked winds of a massive star and a non-accreting pulsar in a binary suffers periodic and random variations of orbital and non-linear dynamical origin. For the 1st time, we simulate in 3 D the interaction of isotropic stellar and relativistic pulsar winds along 1 full orbit, on scales well beyond the binary size. We also investigate the impact of grid resolution and size, and of different EoOs: a gamma-constant ideal gas, and an ideal gas with gamma dependent on temperature. We carry out, with the code PLUTO, relativistic HD simulations in 2 and 3 D of the interaction of a slow wind and a relativistic wind with Gamma=2 along 1 full orbit up to ~100 x …
The internal structure of overpressured, magnetized, relativistic jets
2016
This work presents the first characterization of the internal structure of overpressured steady superfast magnetosonic relativistic jets in connection with their dominant type of energy. To this aim, relativistic magnetohydrodynamic simulations of different jet models threaded by a helical magnetic field have been analyzed covering a wide region in the magnetosonic Mach number - specific internal energy plane. The merit of this plane is that models dominated by different types of energy (internal energy: hot jets; rest-mass energy: kinetically dominated jets; magnetic energy: Poynting-flux dominated jets) occupy well separated regions. The analyzed models also cover a wide range of magnetiz…
The radio afterglow of Swift J1644+57 reveals a powerful jet with fast core and slow sheath
2015
We model the non-thermal transient Swift J1644+57 as resulting from a relativistic jet powered by the accretion of a tidally-disrupted star onto a super-massive black hole. Accompanying synchrotron radio emission is produced by the shock interaction between the jet and the dense circumnuclear medium, similar to a gamma-ray burst afterglow. An open mystery, however, is the origin of the late-time radio rebrightening, which occurred well after the peak of the jetted X-ray emission. Here, we systematically explore several proposed explanations for this behavior by means of multi-dimensional hydrodynamic simulations coupled to a self-consistent radiative transfer calculation of the synchrotron …
On the dynamic efficiency of internal shocks in magnetized relativistic outflows
2009
We study the dynamic efficiency of conversion of kinetic-to-thermal/magnetic energy of internal shocks in relativistic magnetized outflows. We model internal shocks as being caused by collisions of shells of plasma with the same energy flux and a non-zero relative velocity. The contact surface, where the interaction between the shells takes place, can break up either into two oppositely moving shocks (in the frame where the contact surface is at rest), or into a reverse shock and a forward rarefaction. We find that for moderately magnetized shocks (magnetization $\sigma\simeq 0.1$), the dynamic efficiency in a single two-shell interaction can be as large as 40%. Thus, the dynamic efficiency…
Nonlinear stability of relativistic sheared planar jets
2005
The linear and non-linear stability of sheared, relativistic planar jets is studied by means of linear stability analysis and numerical hydrodynamical simulations. Our results extend the previous Kelvin-Hemlholtz stability studies for relativistic, planar jets in the vortex sheet approximation performed by Perucho et al. (2004a,b) by including a shear layer between the jet and the external medium and more general perturbations. The models considered span a wide range of Lorentz factors ($2.5-20$) and internal energies ($0.08 c^2-60 c^2$) and are classified into three classes according to the main characteristics of their long-term, non-linear evolution. We observe a clear separation of thes…
Observational Effects of Anomalous Boundary Layers in Relativistic Jets
2008
Recent theoretical work has pointed out that the transition layer between a jet an the medium surrounding it may be more complex than previously thought. Under physically realizable conditions, the transverse profile of the Lorentz factor in the boundary layer can be non-monotonic, displaying the absolute maximum where the flow is faster than at the jet spine, followed by an steep fall off. Likewise, the rest-mass density, reaches an absolute minimum (coincident with the maximum in Lorentz factor) and then grows until it reaches the external medium value. Such a behavior is in contrast to the standard monotonic decline of the Lorentz factor (from a maximum value at the jet central spine) an…