Weakly quasisymmetric near-axis solutions to all orders

We show that the equations satisfied by weakly quasisymmetric magnetic fields can be solved to arbitrarily high order in powers of the distance from the magnetic axis. This demonstration does not consider force balance. The existence of solutions requires an appropriate choice of parameters, most notably the toroidal current or rotational transform profiles. We do not prove that the expansion converges (it is likely divergent but asymptotic), and thus, the demonstration here should not be taken as definitive proof of the existence of global solutions. Instead, we provide a systematic construction of solutions to an arbitrarily high order.

Automated summary

We demonstrate that weakly quasisymmetric magnetic fields can be solved to arbitrarily high order using powers of the distance from the magnetic axis. However, this does not provide definitive proof of the existence of global solutions, but rather offers a systematic construction method for solutions.