Does the Van der Pol equation with negative parameter explode outside a circle?

Question

Consider the Van der Pol system $$ \mathrm{\frac d {dt}}\begin{bmatrix}x\\y\end{bmatrix} = \begin{bmatrix}y\\\mu(1-x^2)y-x\end{bmatrix} $$ with $\mu < 0$. It attains an asymptotically stable equilibrium at the origin. Is there a circle centered at the origin such that for every trajectory that starts outside the circle, $\|x\| \to \infty$ as $t \to \infty$? It definitely looks like it, but I don't know how I'd prove it.