N o m n ( k , r ) = z n ( ρ ρ ) ρ ρ sin ⁡ ⁡ ( m φ φ ) n ( n + 1 ) P n m ( cos ⁡ ⁡ ( θ θ ) ) e r + sin ⁡ ⁡ ( m φ φ ) d P n m ( cos ⁡ ⁡ ( θ θ ) ) d θ θ 1 ρ ρ d d ρ ρ [ ρ ρ z n ( ρ ρ ) ] e θ θ + m cos ⁡ ⁡ ( m φ φ ) P n m ( cos ⁡ ⁡ ( θ θ ) ) sin ⁡ ⁡ ( θ θ ) 1 ρ ρ d d ρ ρ [ ρ ρ z n ( ρ ρ ) ] e φ φ There is no radial part for magnetic harmonics. For electric harmonics, the radial part decreases faster than angular, and for big ρ ρ can be neglected. We can also see that for electric and magnetic harmonics angular parts are the same up to permutation of the polar and azimuthal unit vectors, so for big ρ ρ electric and magnetic harmonics vectors are equal in value and perpendicular to each other.