Noise-Storm Continua: Power Estimates for Electron Acceleration

We use a generic stochastic acceleration formalism to examine the power Lin (erg s-1) input to non-thermal electrons that cause noise-storm continuum emission. The analytical approach includes the derivation of the Green’s function for a general second-order Fermi process, and its application to obtain the particular solution for the non-thermal electron distribution resulting from the acceleration of a Maxwellian source in the corona. We compare Lin with the power Lout observed in noise-storm radiation. Using typical values for the various parameters, we find that Lin ∼ 1023–1026 erg s-1, yielding an efficiency estimate η ≡ Lout/Lin in the range 10-10 ≲ η ≲ 10-6 for this non-thermal acceleration/radiation process. These results reflect the efficiency of the overall process, starting from electron acceleration and culminating in the observed noise-storm emission.