The Interaction and propagation of magnetic jets in external media

It is commonly accepted that the relativistic jets observed in extragalactic sources like GRBs and AGNs are launched magnetically and are powered by the rotational energy of a central object. Such jets carry most of their energy in the form of electromagnetic Poynting flux. However by the time the ejecta reach the emission zone most of that energy is transferred to relativistic motions of the jet material with a large fraction given to non thermal distribution of particles, which calls for an efficient dissipation mechanism to work within the jet without compromising its integrity. Thus understanding how Poynting dominated jets can dissipate their energy is crucial for modeling these astrophysical objects. In this talk I will present the first self consistent 3D simulations of the formation and propagation of a highly magnetized (Ï>50), relativistic jet in a dense medium. I will show how the magnetic energy in the jet is efficiently dissipated close to the source, reaching a state of equipartition between the magnetic and thermal energies. I will also show how this equilibrium state stabilizes the jet from being further perturbed, and possibly disrupted by magnetic instabilities. I will discuss the implications from these results on the energy emission in GRBs coming from collapsing stars, and on the type of compact objects that power them. I will also present a new scheme that addresses to the dichotomy between FRI and FRII galaxies in AGNs.

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