Approximate expressions are derived (in closed form) for the bounce-averaged transport coefficients (?) and (?) due to synchrotron radiation by a charged particle trapped in a dipole field, where &ggr;-1 is the particle's kinetic energy (in units of rest energy) and y is the sine of its equatorial pitch angle. The expressions for (?) and (?) factor so that (?) is equal to (&ggr;2-1) times a ratio of polynomials in y1,4, while (?) is equal to (1/&ggr;) times a different ratio of polynomials in y1/4. The expressions apply at all values of &ggr; and y for which the adiabatic theory of charged particle motion is a good approximation.