this magnetic field configuration lasts in its current form to allow for a good chance of being observed. Given the toroidal field strength we have found above for Kes 79 ($\sim 10^{14}$ G), its evolution should be dominated by Hall drift, since the Ohmic timescale for a young NS is much longer than the Hall timescale (see Reisenegger et al. 2005; Pons & Geppert 2007; Pons et al. 2009): $$\label{eq:halleq}
{\partial\textbf{B}\over\partial t}=-\nabla\times\left[{c\over 4\pi
    n_e e}\left(\nabla\times\textbf{B}\right)\times\textbf{B}\right],$$ where $n_e$ is the electron number density. The characteristic Hall timescale is $$\label{eq:thall}
t_{\rm Hall}={4\pi n_e e L^2\over c B},$$ where $L$ and $B$ are the typical length scale and field strength. Using values $n_e\sim10^{35}\,\mathrm{cm}^{-3}$, $L\sim0.5H$, with $H$ the crust thickness $\sim1~\mathrm{km}$, and $B\sim2\times10^{14}$ G, we find $t_{\rm Hall}\sim 8~\mathrm{kyr}$. We can further evaluate the Hall timescale as a function of location in the crust via $t_{\rm Hall}\sim
|{\bf B}|/|\partial {\bf B}/\partial t|$. We find that the Hall time scale is greater than $10$ kyr throughout most of the crust, and decreases to a value of $5$ kyr at the edges of the crust. Thus, the magnetic field configuration is stable enough to remain virtually unchanged up to more than the current age of the 