The kinematic evolution of axisymmetric magnetic fields in rotating magnetospheres of relativistic compact objects is analytically studied, based on relativistic Ohm’s law in stationary axisymmetric geometry. By neglecting the poloidal flows of plasma in simplified magnetospheric models, we discuss self-excited dynamos due to the frame-dragging effect (originally pointed out by Khanna & Camenzi...

Pairs of radio emitting jets with lengths up to several hundred kiloparsecs emanate from the central region (the ‘core’) of radio loud active galaxies. In the most powerful of them, these jets terminate in the ‘hotspots’, compact high brightness regions, where the jet flow collides with the intergalactic medium (IGM). Although it has long been established that in their inner (∼parsec) regions t...

High resolution, non-oscillatory, central difference (NOCD) numerical schemes are introduced as alternatives to more traditional artificial viscosity (AV) and Godunov methods for solving the fully general relativistic hydrody-namics equations. These new approaches provide the advantages of Godunov methods in capturing ultra-relativistic flows without the cost and complication of Riemann solvers...

Advection-dominated accretion flows (ADAFs) have a positive Bernoulli parameter, and are therefore gravitationally unbound. The Newtonian ADAF model has been generalized recently to obtain the ADIOS model that includes outflows of energy and angular momentum, thereby allowing accretion to proceed self-consistently. However, the utilization of a Newtonian gravitational potential limits the abili...

A series of simulated maps showing the appearance in total intensity of flows computed using a recently developed relativistic hydrodynamic code (Duncan & Hughes 1994: ApJ, 436, L119) are presented. The radiation transfer calculations were performed by assuming the flow is permeated by a magnetic field and fast particle distribution in energy equipartition, with energy density proportional to t...

Observations over the past decade have verified, beyond reasonable doubt, that most galactic nuclei contain massive black holes. Hole masses are being measured and firm evidence for spin is being sought. Attention is now returning to the study of how gas flows around black holes and how energy is released both from the accreting gas and from the hole itself in the form of radiation, relativisti...

Simple, self-similar, elliptic solutions of non-relativistic fireball hydrodynamics are presented, generalizing earlier results for spherically symmetric fireballs with Hubble flows and homogeneous temperature profiles. The transition from one dimensional to three dimensional expansions is investigated in an efficient manner. Introduction. Recently, a lot of experimental and theoretical efforts...

Collisionless shocks are pervasive in space and astrophysical plasmas and are known to be efficient particle accelerators; however, the microphysics underlying shock formation and particle acceleration is not yet fully understood. The fast progress in laser technology is bringing the study of near-relativistic collisionless shocks into the realm of laboratory plasmas. We use multi-dimensional p...

The extreme hypothesis that essentially all types of ultrarelativistic outflow – specifically AGN jets, pulsar wind nebulae and GRB –are electromagnetic, rather than gas dynamical, phenomena is considered. It is suggested that the observed emission is generated in regions of high current density where global instabilities drive a turbulence spectrum that is ultimately responsible for the partic...

I will discuss several issues related to the acceleration, collimation, and propagation of jets from active galactic nuclei. Hydromagnetic stresses provide the best bet for both accelerating relativistic flows and providing a certain amount of initial collimation. However, there are limits to how much "self-collimation" can be achieved without the help of an external pressurized medium. Moreove...