[Phys-seminars] 2017-12-06 Astrophysics and Cosmology Seminar

zitrin zitrin at bgu.ac.il
Thu Nov 30 11:09:45 IST 2017


Astrophysics and Cosmology Seminar

 DATE: 06-12-17

 TIME: 11:15

 PLACE: Physics building (#54) room 207

TITLE: 
Jets formation and collimation in AGNs and GRBs

SPEAKER: 
Dr. Noemie Globus, The Hebrew University of Jerusalem

ABSTRACT/COMMENTS: 
Two competing jet formation mechanisms have been widely discussed in the literature: magnetic extraction of the spin down power of a Kerr black hole, and outflow formation via plasma injection above the black hole horizon. These two processes are commonly treated under idealized conditions : models of Blandford- Znajek jets usually invoke the force-free limit and ignore loading of magnetic field lines, whereas pressure-driven jets are usually constructed within the pure hydrodynamic limit. In general, however, both processes might be at work, and it is desirable to characterize the interplay between them. I will present semi-analytic models for the formation of magnetic jets around rotating black hole including loading of the magnetic field lines, and discuss, in the case of GRBs, the total power of an outflow powered both by Blandford-Znajek and neutrino annihilation. The second part of my talk will be devoted to jet collimation. I will present semi-analytic models for the c
 onfinement of a highly magnetized jet by a hydrodynamic wind emanating from the upper layers of the accretion disk surrounding the black hole. I will discuss the jet collimation efficiency for different configurations of the wind streamlines and different distributions of the mass effluxion rate. I will suggest that a disk wind from the RIAF may be responsible for the collimation of the jet in M87.


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