Mathematica does all its computations in an orthonormal basis. You simply need to specify what coordinate system you're working in. So for your example, you just multiply by {0,0,1}{0, 0, 1}:
e[r_, θ_, ϕ_, t_] := (Sin[θ]/r)[Cos[r - t] - Sin[r - t]/r] {0, 0, 1} ApprentlyApparently this is a pure wave in vacuum, as the divergence is zero:
Div[e[r, θ, ϕ, t], {r, θ, ϕ}, "Spherical"] (* 0 *) Similarly, a pure ColoumbCoulomb electric field would be
col[r_, θ_, ϕ_] := {1/r^2, 0, 0} Div[col[r, θ, ϕ], {r, θ, ϕ}, "Spherical"] (* 0 *) I suggest you look at the the tutorials tutorial/VectorAnalysis and tutorial/ChangingCoordinateSystems and the functions linked therefrom for more.