Samaporn Tinyanont edited untitled.tex  almost 8 years ago

Commit id: a3a4933084f773065e8563da791f6c378ba0f317

deletions | additions      

       

Magnetars are neutron Neutron  stars typically have magnetic fields of $\sim 10^{12} \rm \ G$. However, if a neutron star's rotation period is comparable to the convective overturn time, magnetic fields can be amplified by helical motion in a mechanism called mean field dynamo. These highly magnetized neutron stars, magnetars, are  born with short periods of $\sim$ 1 ms, which allow them to support an efficient $\alpha-\Omega$ dynamo, resulting in large  magnetic dipole fields of $10^{14}-10^{15} \rm \ G$. This field strength is higher than that of normal neutron stars by a factor of $\sim 10^2$. They G$ \cite{Duncan_1992}.  %They  were first proposed by \cite{Duncan_1992} to explain Soft Gamma Repeaters (SGRs). A magnetar of mass $1.4 M_{\odot}$, $R = 10 \ \rm km$, and $P = 1 \ \rm ms$ has a rotational energy of \begin{equation}  E_{\rm rot} = I \omega^2 /2 = \dfrac{1}{5}MR^2 \left(\dfrac{2\pi}{P}\right)^2 \simeq 4.4 \times 10^{51} \ \rm erg  \end{equation}