Electric dipole radiation
= Electric dipole radiation
For a localized source whose size is small compared with its radiation wavelength, the radiation fields of its electric dipole moment $p$ are
$$
E_{\rm rad}=\frac{\mu_0}{4\pi R}\widehat R\times(\widehat R\times\ddot p(t-R/c)),
\qquad
B_{\rm rad}=\frac1c\widehat R\times E_{\rm rad}.
$$
Their total instantaneous power is
$$
\mathcal P=\frac{\mu_0}{6\pi c}|\ddot p(t-R/c)|^2.
$$