Evoltuion of Magnetic Fields in Neutron Stars

[ImaLooser]

I have been reading research papers on this topic, such as

Evolution of the magnetic field in magnetars
J. Braithwaite and H. C. Spruit 2006
http://www.aanda.org/index.php?opti...doi&doi=10.1051/0004-6361:20041981&Itemid=129

This is informative but takes the evolution through only the first thousand years or so. They do not deal with what occurs after the neutron star becomes superconductive.

My understanding, such as it is, is this. The neutron star is created in a supernova with temperatures of trillions of degrees. At the this time the crust is about 1.5km of iron and highly conductive, the core neutrons and less conductive. The neutron star inherits a portion of the magnetic field of the parent star. The field has one hundred seconds or so to relax to mostly a twisted torus internal to the star with the rest a poloidal field. The crust then solidifies, locking the portion of the field in the crust into place. The portion of the field in the interior continues to diffuse. The stress between the crust and core can become so great that the crust ruptures.

This is as far into the evolution as that paper seems to go.

After the star cools for some time (one year?) the core becomes superconductive. It is a Type II superconductor and the magnetic field is strong enough that quantum flux tubes penetrate the core.

After more time (1000 years?) the core is cool enough to become a combination of a neutron superfluid, a proton superfluid, and an ordinary electron fluid. Within the core appears an array of rotational vertices. At this point my view becomes hazy. Is a magnetic field generated in the core, what is its shape, how strong is it?

My second question is, how does the magnetic field in the core find an equilibrium? By the energy slowing dissipating into the crust? Since the crust is very rigid this would be a very slow process. Surely the magnetic field in the superconductive core does not increase without bound.

I suspect that this forum is not the place for this question. Any suggestions as to where an answer might be found?

 

[eljose79]

Thank you for sharing your thoughts and questions on the evolution of magnetic fields in magnetars. As a scientist studying this topic, I would like to offer some insights and address your questions.

Firstly, the paper you mentioned by Braithwaite and Spruit indeed provides valuable information on the early evolution of magnetic fields in magnetars, but as you mentioned, it only covers the first thousand years or so. This is because the evolution of magnetic fields in neutron stars is a complex and ongoing process, and it is challenging to accurately model and predict the behavior of the magnetic field over long periods of time.

As for your understanding of the formation and initial evolution of magnetars, it is mostly correct. However, I would like to clarify a few points. The neutron star inherits its magnetic field from the parent star, but it is not a direct transfer. Instead, the magnetic field is amplified and twisted during the supernova explosion, resulting in a much stronger and more complex field in the neutron star. Also, the neutron star crust is not entirely conductive, and the core is not entirely non-conductive. Both regions have varying degrees of conductivity, and the magnetic field interacts differently with each.

In terms of the evolution of the magnetic field in the superconducting core, it is still an active area of research, and there is no consensus on the exact mechanisms at play. However, it is believed that the magnetic field in the core does not increase without bound, as you correctly pointed out. The energy dissipation processes in the crust, such as crustal cracking and starquakes, can help to regulate the magnetic field and prevent it from growing too strong. Additionally, the interaction between the magnetic field and the superfluids in the core can also play a role in reaching an equilibrium state.

Regarding your second question on how the magnetic field in the core finds an equilibrium, as mentioned earlier, there is ongoing research on this topic. Some studies suggest that the equilibrium is reached through the dissipation of energy into the crust, while others propose that the superfluids in the core play a more significant role in regulating the magnetic field. It is a complex and dynamic process that requires further investigation.

In terms of finding answers to your questions, I would suggest looking into recent research papers on the subject and perhaps reaching out to the authors for more information. You could also consider attending conferences or workshops on neutron stars and magnetars, where you can interact with experts in the