Consider the Laplacian of the x component of the magnetic field ∇ ∇ 2 B x = ∂ ∂ 2 B x ∂ ∂ x 2 + ∂ ∂ 2 B x ∂ ∂ y 2 + ∂ ∂ 2 B x ∂ ∂ z 2 = ∂ ∂ ∂ ∂ x ∂ ∂ B x ∂ ∂ x + ∂ ∂ ∂ ∂ y ∂ ∂ B x ∂ ∂ y + ∂ ∂ ∂ ∂ z ∂ ∂ B x ∂ ∂ z