Timeline for Magnetic decay versus rotation braking of neutron stars
Current License: CC BY-SA 3.0
6 events
| when toggle format | what | by | license | comment | |
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| Aug 3, 2017 at 16:18 | comment | added | Cham | There's nothing wrong with that theory. It's just one scenario among several others, that are also interesting. The magnetic diffusion that you described is equivalent to an exponentially decaying magnetic moment : $\mu(t) = \mu(0) \, e^{-\, \lambda \, t}$, which can also accelerate the spin, for some values of $\lambda$ (diffusion decay parameter) ! I also noticed that we can define a tilted oblate ellipsoid (the dipolar magnetic field may distords a bit the source), which will make the tilt angle parameter $\alpha$ to also decrease with time. | |
| Aug 3, 2017 at 16:01 | comment | added | Thomas | To come back to the original question: We still have to figure out what determines the evolution of pulsar spin and magnetic field. What's wrong with the standard story (repeated in my answer), that the spin evolves because rotational energy powers the emission, and the magnetic field evolves by diffusion? | |
| Aug 3, 2017 at 15:58 | comment | added | Thomas | Isn't that what I said? You have to split the field into static (inside the light cylinder) and radiation (outside)? | |
| Aug 2, 2017 at 12:16 | comment | added | Cham | No, the total energy and angular momentum are not conserved, there's emission of radiation to infinity. Conservation applies only to isolated (or closed) systems, which is not the case here. This is exactly the essence of the Poynting theorem : \begin{equation} \frac{dE}{dt} = \oint_{\mathcal{S}} \vec{\boldsymbol{\mathrm{S}}} \cdot d\vec{\boldsymbol{\mathrm{A}}} = \text{power of electromagnetic energy loss to infinity,}\end{equation} where $E = E_{\text{mec}} + \int_{\mathcal{V}} u_{EM} \, d^3 x$ is the total energy (mechanical and electromagnetic) of the system emitting the radiation. | |
| Aug 2, 2017 at 6:52 | comment | added | Thomas | I'm not sure I understand your point. The total energy and angular momentum are obviously conserved, $dE/dt=0$, $dL/dt=0$. You could try to split the field part into a "static" field, co-rotating with the star, and a radiation field that carries away energy and angular momentum | |
| Aug 1, 2017 at 16:04 | history | answered | Cham | CC BY-SA 3.0 |