Formation of relativistic MHD jets: stationary state solutions & numerical simulations

We discuss numerical results of relativistic magnetohydrodynamic (MHD) jet formation models. We first review some examples of stationary state solutions treating the collimation and acceleration process of relativistic MHD jets. We provide an a posteriori check for the MHD condition in highly magnetized flows, namely the comparison of particle density to Goldreich-Julian density. Using the jet dynamical parameters calculated from the MHD model we show the rest-frame thermal X-ray spectra of the jet, from which we derive the overall spectrum taking into account a variation of Doppler boosting and Doppler shift of emission lines along the outflow. Finally, we present preliminary results of relativistic MHD simulations of jet formation demonstrating the acceleration of a low velocity (0.01c) disk wind to a collimated high velocity (0.8c).Comment: 6 pp, 5 figs; Invited talk at High Energy Processes in Relativistic Jets, Dublin, 2007, in pres

Theoretical thermal X-ray spectra of relativistic MHD jets

Highly relativistic jets are most probably driven by strong magnetic fields and launched from the accretion disk surrounding a central black hole. Applying the jet flow parameters (velocity, density, temperature) calculated from the magnetohydrodynamic (MHD) equations, we derive the thermal X-ray luminosity along the inner jet flow in the energy range 0.2-10.1 keV. Here, we concentrate on the case of Galactic microquasars emitting highly relativistic jets. For a 5 solar masses central object and a jet mass flow rate of 10^{-8} solar masses/year we obtain a jet X-ray luminosity L_x ~ 10^{33} erg\sec. Emission lines of Fe XXV and Fe XXVI are clearly visible. Relativistic effects such as Doppler shift and Doppler boosting were considered for different inclinations of the jet axis. Due to the chosen geometry of the MHD jet the inner X-ray emitting part is not yet collimated. Therefore, depending on the viewing angle, the Doppler boosting does not play a major role in the total spectra.Comment: 7 pages, 12 eps figures, 1 table, LaTeX2e file. Accepted for publication in Astronomy & Astrophysics, [email protected], [email protected], [email protected]. The original version of the manuscript is available at http://www.aip.de/~ememola and http://www.aip.de/~cfend