In the case of a point charged particle q moving at a constant velocity v, Maxwell's equations give the following expression for the electric field and magnetic field: E = q 4 π π ε ε 0 1 − − β β 2 ( 1 − − β β 2 sin 2 ⁡ ⁡ θ θ ) 3 / 2 r ^ ^ ′ | r ′ | 2 H = v × × D B = 1 c 2 v × × E where