Noise storm continua: power estimates for electron acceleration

Abstract

We use a generic stochastic acceleration formalism to examine the power Lin (erg s −1 ) input to nonthermal 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 nonthermal 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 ∼ 1023−26 erg s −1 , yielding an efficiency estimate η ≡ Lout/Lin in the range 10−10 ∼ < η ∼ < 10−6 for this nonthermal acceleration/radiation process. These results reflect the efficiency of the overall process, starting from electron acceleration and culminating in the observed noise