Abrupt line-current wavefront singularity
= Abrupt line-current wavefront singularity
The ideal fields after instantaneous switching behave as $E_z,H_\phi\propto(t-r/c)^{-1/2}$ near arrival, and the radial <Poynting vector> as $(t-r/c)^{-1}$. A finite switching rise time smooths the ideal front; the singular solution does not represent a finite-energy real pulse.