Effect of Synchrotron Losses on Multiple Diffusive Shock Acceleration

Abstract

AbstractThe effect of synchrotron losses on diffusive shock acceleration (DSA) at many shocks is treated numerically. Synchrotron losses determine a maximum energy to which electrons can be accelerated through DSA, and this is referred to as the synchrotron cutoff, pc. The distribution of accelerated electrons after many shocks is found (a) for a distribution injected at the initial shock, to tend to a plateau [f(p) independent of p ≲ 0·1pc], and (b) for the cumulative distribution from injection at each shock to tend to f(p) ∝ p–b with b ≈ 3 well below the synchrotron cutoff with a peak in the slope (bmin ≈ 2) at p ≲ 0·1pc. It is suggested that the latter result might account for the flat synchrotron spectra observed in some Galactic Centre sources.