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- A Hujeirat, R Blandford
- 2003

A self-similar solution for the 3D axi-symmetric radiative MHD equations, which revisits the formation and acceleration of accretion-powered jets in AGNs and microquasars, is presented. The model relies primarily on electromagnetic extraction of rotational energy from the disk plasma and forming a geometrically thin super-Keplerian layer between the disk… (More)

- A Hujeirat, M Camenzind, M Livio
- 2002

Low cooling plasmas associated with large kinetic energies are likely to be the origin of the kpc-extended and well collimated extra-galactic jets. It is proposed that jets are launched from a layer, governed by a highly diffusive, super-Keplerian rotating and thermally dominated by virial-hot and magnetized ion-plasma. The launching layer is located… (More)

- A. Hujeirat
- 1998

We investigate the effects of radiation and magnetic fields on the formation, structure, and stability of the axisymmetric shock and settling flow produced by accreting gas initially directed towards a non rotating stellar surface from a polar column with free-fall speed. We perform one dimensional reference calculations as well as two dimensional… (More)

- A. A. Hujeirat
- Computer Physics Communications
- 2005

We present a hierarchical approach for enhancing the robustness of numerical solvers for modelling radiative MHD flows in multi-dimensions. This approach is based on clustering the entries of the global Jacobian in a hierarchical manner that enables employing a variety of solution procedures ranging from a purely explicit time-stepping up to fully implicit… (More)

- Ahmad Hujeirat
- 2003

Most powerful jets are observed to emanate from accreting black hole systems. Recent quasi-stationary radiative MHD calculations reveal that jet-launching start in the innermost region of a transition layer (-TL), which is located between the disk and the corona. The plasma in the TL is dominated by virial-hot protons, advective, highly magnetic-diffusive… (More)

- A Hujeirat, M Camenzind
- 2000

Our quasi-steady 2D numerical radiative hydrodynamical investigations of two-temperature accretion flows around black holes indicate that standard disks are thermally and hydrodynamically stable against transition to optically thin disks at large radii. Optically thin disks cool sufficiently rapid at large radii inducing a vertical collapse and forming… (More)

- A A Hujeirat, B W Keil, P P And Hilscher, Landessternwarte Zah, Heidelberg-Königstuhl
- 2009

Aims. A numerically stable and accurate advection scheme for modeling shock fronts moving at ultra-relativistic speeds is fundamentally important for understanding the thermodynamics of jets emanating from the vicinity of relativistic objects and the origin of the high gamma-rays. Methods. In this paper we present a spatially third-order accurate advection… (More)

- A. Hujeirat, B. W. Keil
- 2008

We adopt the Boyer-Lindquist coordinates and formulate the hydrodynamical equations in the fixed background of a Kerr black hole. The set of equations are solved implicitly using the hierarchical solution scenario (HSS). The HSS is efficient, robust and enables the use of a variety of solution procedures that range from a purely explicit up to fully… (More)

- A Hujeirat, M Livio
- 2003

The powerful and highly collimated jets observed in active galactic nuclei and μ−quasars are likely to be connected to the accretion phenomena via disks. Based on theoretical arguments and quasi-stationary radiative MHD calculations, a model for accretioninduced jet is presented. It is argued that accretion disks around BHs consist of 1) a cold,… (More)

- A. A. Hujeirat, Friedrich-K. Thielemann
- Informatik-Spektrum
- 2009

Einleitung Kurz nach dem zweiten Weltkrieg waren Rudolf Kippenhahn, damals in Erlangen/Bamberg und später Professor in Göttingen bzw. Direktor des Max-Planck-Instituts für Astrophysik, sowie Martin Schwarzschild, der in Göttingen promoviert hatte und später Professor in Princeton wurde, die ersten Pioniere, die zur Berechnung der Struktur und… (More)