2026-07-072026-07-07http://salesiana.dossiersoluciones.com/handle/123456789/142238We derive analytic formulas for the power output and critical frequency of radiation by electrons accelerated by relativistic kinetic Poynting flux, and validate these results with Particle-In-Cell plasma simulations. We find that the in-situ radiation power output and critical frequency are much below those predicted by the classical synchrotron formulae. We discuss potential astrophysical applications of these results.25 pages, 11 figures, revised paper resubmitted to Astrophysical JournalAstrophysicstext