The Laplacian of the y component of the magnetic field B y field and the Laplacian of the z component of the magnetic field B z can be calculated analogously. Alternatively, one can use the identity ∇ ∇ 2 B = ∇ ∇ ( ∇ ∇ ⋅ ⋅ B ) − − ∇ ∇ × × ( ∇ ∇ × × B ) , where both terms in the parentheses vanish.