= Liénard-Wiechert field
{c}
The <Liénard-Wiechert field> is the <electric field> and <magnetic field> obtained from the retarded potentials of a moving point charge. In the nonrelativistic radiation zone, the electric radiation field is $\mathbf E_{\rm rad}=q\widehat{\mathbf n}\times(\widehat{\mathbf n}\times\mathbf a)/(4\pi\epsilon_0c^2R)$ at <retarded time>. Its outgoing <Poynting vector> integrates to the <Larmor formula>. Coulomb and induction fields must also be retained when a near-field calculation is required.
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