149 research outputs found
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
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