Knotted structures in high-energy Beltrami fields on the torus and the sphere

Let S be a finite union of (pairwise disjoint but possibly knotted and linked) closed curves and tubes in the round sphere S^3 or in the flat torus T^3. In the case of the torus, S is further assumed to be contained in a contractible subset of T^3. In this paper we show that for any sufficiently large odd integer \lambda there exists a Beltrami field on S^3 or T^3 satisfying curl u = \lambda u and with a collection of vortex lines and vortex tubes given by S, up to an ambient diffeomorphism.