Session 3HE: AGN/BH Jet Dynamics

Astrophysical Jets

I will show that the assumption that the acceleration and collimation mechanisms of jets are the same in all classes of astrophysical objects which are observed to produce jets, can lead to interesting conclusions. Jets have now been observed in: AGNs, young stellar objects, x-ray binaries, black hole x-ray transients, symbiotic systems, supersoft x-ray sources, pulsars, and possibly planetary nebulae and recurrent novae. I will attempt to identify the necessary ingredients for the production of powerful jets, and will suggest critical observations that can test the ideas presented in this talk.   

3-D MHD Simulations of Astrophysical Jets

Jets and outflows are ubiquitous among the accretion process in a variety of astrophysical objects. Global three-dimensional (3-D) magnetohydrodynamic (MHD) simulations of accretion flows have revealed the generation of jets by the emergence of a magnetic tower. In other words, the magnetic interaction associated with stars and/or accretion disks is a promising universal mechanism of launching jets. However, photon spectra of accretion flows and jets in some microquasars display some serious problems. When spetrum is dominated by non-thermal emissions, a mildly relativistic steady jet is observed. On the other hand, when spectrum is dominated by thermal emissions, no jet is observed. Remarkably, during a transition from a non-thermal state to a thermal state, a ultra-relativistic transient jet is observed. Therefore, the radiation in a magnetized accretion flow is a key to understand the formation of jets. In this talk, we present 3-D MHD simulations of magnetic tower jets and also 3-D radiation transfer (RT) simulations of magnetic tower jets. The possible connection between the emergence of magnetic tower jets and the evolution of radiation properties will be discussed.   

Episodic ``Magnetic Tower'' Plasma Jets in a Laboratory Experiment

We will present experimental results on formation of supersonic magnetically driven plasma jets with dimensionless parameters similar to those in proto-stellar jets. The jets are driven by the pressure of the toroidal magnetic field and the plasma beta in these jets is of the order of unity [1,2]. The experimental configuration allows generation of several episodes of the magnetic tower jet eruptions. The subsequent magnetic bubbles have higher propagation velocities and are catching up the previously ejected, producing shocks. These experiments suggest that periodic formation of magnetic tower jets in the astrophysical situations could be responsible for some of the variability of the astrophysical jets. The experiments are scalable to astrophysical flows in that critical dimensionless numbers such as the plasma collisionality, the plasma beta and the magnetic Reynolds number are all in the astrophysically appropriate ranges. The experimental results will be compared with computer simulations performed with laboratory plasma codes and with astrophysical codes. [1] S.V. Lebedev et al., Mon. Not. R. Astron. Soc., 361 97 (2005) [2] A. Ciardi et al., Physics of Plasmas, 14, 056501 (2007). In collaboration with: A. CIARDI, F.A. SUZUKI-VIDAL, S.N. BLAND, S.C. BOTT, J.P. CHITTENDEN, G. HALL, A. HARVEY-THOMSON, A. MAROCCHINO, A. FRANK, E. G. BLACKMAN, T. RAY, C. STEHLE