Formation of jets with accretion disks at black holes

[haushofer]

TL;DR

Looking for resources on the formation of jets at black holes

Dear all,

I'm going to give a course about black holes at an astrophysics association. The public will consist mainly of lay persons, perhaps wit a little bit of physics background. My background in General Relativity is good, but my background in astrophysics at bit less. My question is if you know about some good online resources/lecture notes about the formation of jets (and accretion discs) around black holes, and the mechanisms behind those jets launching charged particles. Is there an intuitive/easy way to understand how those jets form in the first place? Many thanks.

 

[Vanadium 50]

This may not be so easy - I don't think the phenomenon is completely understood.

At first order, things are simple. If the source is surrounded by an orbiting disk, you get absorption in the disk-ward direction and thus transmission perpendicular to that. The problem is that jets seem to be narrower and more energetic than that simple model.

I don't think there is any model that reproduces all the observed features. Shock seems to be involved, ant multi-component fluids (electrons do this, ions do that). Certainly magnetic fields by themselves won't do the trick.

Wasn;t there an Annual Review on jets a few years back?

 

[Hyperfine]

I concur that your task is far from simple. The only postulated mechanisms that I am aware of for formation of relativistic jets are the Penrose process and the Blandford-Znajek mechanism.

The first is based on frame-dragging, the second on a magnetized accretion disk with rotational contortions of the field lines.

 

[haushofer]

I concur that your task is far from simple. The only postulated mechanisms that I am aware of for formation of relativistic jets are the Penrose process and the Blandford-Znajek mechanism.

The first is based on frame-dragging, the second on a magnetized accretion disk with rotational contortions of the field lines.

Mmmm, yes, after some reference searching I get the feeling that my hope of a sketch of the physical process "on the back of an enevelope" is a bit naive. I was hoping to get some feeling of why there are jets in the first place, and how its direction(s) roughly are determined.

 

[haushofer]

This may not be so easy - I don't think the phenomenon is completely understood.

At first order, things are simple. If the source is surrounded by an orbiting disk, you get absorption in the disk-ward direction and thus transmission perpendicular to that. The problem is that jets seem to be narrower and more energetic than that simple model.

I don't think there is any model that reproduces all the observed features. Shock seems to be involved, ant multi-component fluids (electrons do this, ions do that). Certainly magnetic fields by themselves won't do the trick.

Wasn;t there an Annual Review on jets a few years back?

You mean

https://www.annualreviews.org/doi/pdf/10.1146/annurev-astro-081817-051948
?
That's behind a paywall, unfortunately.

 

[Vanadium 50]

behind a paywall

Unless you need it now, that's what libraries are for,

But why not just giove them the first order explanation perhaps adding "reality is far more complicated and not entirely understood".

 

[Hyperfine]

You mean

https://www.annualreviews.org/doi/pdf/10.1146/annurev-astro-081817-051948
?
That's behind a paywall, unfortunately.

That review article is available at arXiv.org.
https://arxiv.org/abs/1812.06025

 

[haushofer]

That review article is available at arXiv.org.
https://arxiv.org/abs/1812.06025

Thanks! Silly I didn't check that for myself. Greatly appreciated.

 

[haushofer]

Unless you need it now, that's what libraries are for,

But why not just giove them the first order explanation perhaps adding "reality is far more complicated and not entirely understood".

Yeah, sure, it's mostly for my own understanding. I'm just a bit surprised that my intuition falls short here, so I guess I learned something new :P

 

[vanhees71]

You mean

https://www.annualreviews.org/doi/pdf/10.1146/annurev-astro-081817-051948
?
That's behind a paywall, unfortunately.

https://arxiv.org/abs/1812.06025

A great browser extension is "Unpaywall", hinting to legal free sources (most often arXiv) of journal articles.

https://unpaywall.org/products/extension

 

[Hornbein]

Neutron stars also have relativistic jets. A black hole is not a requirement. One may easily find images of the jets from the neutron star in the Crab Nebula. We know it has a neutron star because it is a pulsar. A black hole cannot be a pulsar.

I know that there is as yet no completely satisfactory explanation of relativistic jets. That is, an entirely successful model has yet to be built.

 

[sophiecentaur]

Old habits die hard - likewise old models. People still say that nothing can get out of a black hole but Hawking changed that many years ago (1970s).