In an attempt to make the present summary comprehensible yet sufficiently concise I will risk some over-simplification: further details are given in Seaton (1997, 1998 — Papers I and II).In a star let Fv dv be the outward flux of radiant and let an atom of element k present an effective area of σv(k) for absorption of radiation. Then the momentum absorbed per atom and per-unit area and unit time is G(k) = (1/c) ∫ Fvσv(k) dv which is just the force acting on the atom. The radiative acceleration is grad(k) = G(k)/M(k) where M(k) is the atom’s mass.
On radiative acceleration in spine–sheath structured blazar jets