What is Magnetic Buoyancy and How Does it Affect Neutron Stars?

[ImaLooser]

Could anyone suggest an online-reference about the basics? I'm trying to figure out whether there would be such buoyancy in a complicated situation.

 

[Astronuc]

Could anyone suggest an online-reference about the basics? I'm trying to figure out whether there would be such buoyancy in a complicated situation.

With respect to a plasma?

 

[Bobbywhy]

Could anyone suggest an online-reference about the basics? I'm trying to figure out whether there would be such buoyancy in a complicated situation.

Is there some reason why the "complicated situation" is not given? A complete description of the question(s) you are asking would make more reasonable and useful responses possible.

So, as a "stab in the dark" or "trying to hit some target while partially blindfolded", here are a few references where you can study magnetic bouyancy:

http://solar.physics.montana.edu/munoz/REU/Buoyancy.html
http://arxiv.org/abs/1102.3598
www.soe.ucsc.edu/~brummell/.../cline_brummell_cattaneo_2003b.pd ...
http://iopscience.iop.org/0004-637X/727/2/112

 

[ImaLooser]

Is there some reason why the "complicated situation" is not given?

I would like to figure out what sort of magnetic buoyancy would be for a knotted quantum magnetic flux tube in the superconductive/superfluid core of a neutron star. I have asked several such questions here in the past with n reply, so this time a different approach.

I know nothing about magnetic buoyancy. I searched the Internet and unusually there is nothing basic, other than stating an equation that shows that the internal pressure is less than the external. Well, why is that? What is the derivation of this equation? Does this equation always apply? Is it possible to have a large pressure gradient like that in a superfluid? Since magnetic fields in neutron stars are very strong (up to 10^15 Gauss and possibly 10^18) and the equation has a squared term the pressure differential would be extremely large.

 

[Bobbywhy]

ImaLooser, I also know nothing about magnetic buoyancy. I also know nothing about the MHD inside neutron stars. I did, however, search using your more detailed description and found a few references that may assist you in your search. Will you let us know if these help?

Behaviour of Magnetic Tubes in Neutron Star’s Interior
R.S.Singh1, B.K.Sinha2 and N.K.Lohani3, 31 Dec 2002
http://arXiv:astro-ph/0212579v

An Introduction to Magnetic Fields in Neutron Stars
Luciano Rezzolla_SISSA, International School for Advanced Studies and INFN, Trieste, Italy. Department of Physics and Astronomy, Louisiana State University, Baton Rouge, LA 70803 USA
http://sfb.aei.mpg.de/School04/Abstracts.html

Do Vortex Filaments in a Superfluid Neutron Star Produce Gravimagnetic Forces ?
Herbert BALASIN and Werner ISRAEL, 10 Jun 1997
http://arXiv:gr-qc/9706023v1

“Besides the force exerted by the neutron vortices, there
exist other forces which act onto the fluxoids in the Neutron Star
core. The buoyancy force, acting per unit length of the
fluxoid, is given by (Muslimov & Tsygan 1985)”
Muslimov, A., & Tsygan, A. 1985, SvAL, 11, 80

Toward the Quasi Steady State Electrodynamics of a Neutron Star
A. MUSLIMOV 1 AND A. K. HARDING
THE ASTROPHYSICAL JOURNAL, 485:735 746, 1997 August 20
http://iopscience.iop.org/0004-637X/485/2/735/fulltext/35609.text.html

On the nature of the residual magnetic fields in millisecond pulsars
D. Konenkov; and U. Geppert
http://arXiv:astro-ph/0104339

The effect of the neutron star crust on the evolution of a core magnetic field
D. Konenkov (1), U. Geppert (2) ((1) A.F.Ioffe Institute of Physics and Technology, (2)Astrophysikalisches Institut Potsdam)
http://arXiv:astro-ph/9910492

 

[ImaLooser]

Thanks. I found an equation for buoyancy in a neutron star. It is quite different from that for an ordinary star. I still don't understand why there is any buoyancy at all.

 

[Bobbywhy]

Using Google search terms “magnetic buoyancy neutron star Parker instabilities” I found two papers which discuss buoyancy. If I had more time I would go to some of their referenced papers also.

The Astrophysical Journal, 557:958-966, 2001 August 20
© 2001. The American Astronomical Society. All rights reserved. Printed in U.S.A.
Magnetic Screening in Accreting Neutron Stars
Andrew Cumming , Ellen Zweibel ,1 and Lars Bildsten 2

6. BUOYANCY INSTABILITY
We now investigate the stability of the steady state magnetic profiles to buoyancy instabilities. We first consider interchange and Parker instabilities in § 6.1 before including the effects of thermal diffusion in § 6.2.
6.1. Interchange and Parker Instabilities
The simplest case to consider is the interchange instability in which a magnetic field line and associated fluid is lifted vertically, maintaining pressure balance with its surroundings. If the new density is less than that of the surrounding fluid, it is buoyantly unstable.
http://iopscience.iop.org/0004-637X/557/2/958/fulltext/The Astrophysical Journal 671 (2007) 1726
The American Astronomical Society. All rights reserved. Printed in U.S.A.
The Magnetic Rayleigh-Taylor Instability in Three Dimensions
James M. Stone and Thomas Gardiner

A number of studies of magnetic buoyancy instabilities in three dimensions have been reported, both in the context of the emergence of new magnetic flux from the solar photosphere (Wissink et al. 2000; Fan 2001; Isobe et al. 2005, 2006), and the nonlinear evolution of the Parker instability in the Galactic disk (Kim et al. 2002; Kosiński & Hanasz 2007). In these studies, the magnetic field is strong enough for the ratio of thermal to magnetic pressure , so that the magnetic field not only plays a significant role in the support of the initial equilibrium state, but also is responsible for driving buoyant motions. In contrast, we study weak fields in the sense that , so that the magnetic field plays almost no role in the vertical equilibrium, and the RTI is driven by the buoyancy of the fluid. Our goal is to study how magnetic fields affect the evolution of the classical RTI.
http://iopscience.iop.org/0004-637X/671/2/1726/fulltext/72530.text.html