PoS - Proceedings of Science
Volume 306 - XII Multifrequency Behaviour of High Energy Cosmic Sources Workshop (MULTIF2017) - Jet Sources and Gamma-Ray Bursts
The astrophysical jets (again): as the most complicated inorganic machines known to us
W. Kundt
Full text: pdf
Pre-published on: March 16, 2018
Published on: May 30, 2018
In this talk (at Mondello), I attempt to sketch again my understanding of the universal working scheme of all the astrophysical jet sources, or 'bipolar flows', on both stellar and galactic scales, also called 'microquasars', and 'quasars'. A crucial building block will be their medium (whenever bare): extremely relativistic e$^{\pm}$-pair plasma performing quasi loss-free ExB-drifts through self-rammed channels, whose guiding equipartition E- and B-fields convect the electric potential necessary for eventual single-step post-acceleration, at their 'knots' and terminating 'hotspots', or 'heads'. These electromagnetic fields convect half of the jet's power. The indispensible pair plasma is generated in magnetospheric reconnections of the heavy central rotator. For this reason alone, black holes cannot possibly serve as jet engines.

During its passage from subsonic to supersonic propagation, still inside its deLaval nozzle, the escaping relativistic pair-plasma passes from a relativistic Maxwellian distribution (almost) to that of a (mono-energetic) Deltafunction, of (uniform) Lorentz-factor $\gamma = 10^{2\pm 2}$. Clearly, this transition in velocity distribution -- in transit through the deLaval nozzle -- is not loss-free; it turns the jet engine into a transient powerful $\gamma$-ray emitter, with photon frequencies reaching up to $\lesssim $10$^{26}$Hz, (corresponding to electron Lorentz factors $\gamma \lesssim 10^{6}$), see page 120 of [Kundt \& Krishna, 2004].

So far, until [Kundt, 2015], all the jets were treated as though propagating in vacuum, as "bare jets". New in 2015 was an allowance for an embedding medium of non-negligible density, most notably encountered in SS 433 (with its fast-moving X-ray and optical spectral lines), but likewise in our Galactic twin jet. Such an embedding medium, gas or plasma, will try to penetrate into the jet channels, but will instead be ionised, expelled, and dragged along by the streaming, extremely relativistic pair plasma, in the form of subrelativistically comoving channel-wall material. In this way, bare jets are converted into (line- and continuum-) emitting "dressed jets". Unfortunately, in 2015, I had been a bit rush: The generalisation from 'bare' to 'dressed' is not exactly straight-forward, and should respect stability constraints, in order to (again) be unique; which I hope to present below, in this my second approach.
DOI: https://doi.org/10.22323/1.306.0075
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