Noise storm continua: power estimates for electron acceleration

Abstract

We use a generic stochastic acceleration formalism to examine the power $L_{\mathrm{in}}$ ($\mathrm{erg}{\mathrm{s}}^{-1}$) 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 $L_{\mathrm{in}}$ with the power $L_{\mathrm{out}}$ observed in noise storm radiation. Using typical values for the various parameters, we find that $L_{\mathrm{in}}\sim 10^{23-26}$ $\mathrm{erg}{\mathrm{s}}^{-1}$, yielding an efficiency estimate $\eta \equiv L_{\mathrm{out}}/L_{\mathrm{in}}$ in the range $10^{-10} \lsim η\lsim 10^{-6}$ 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 storm emission.

Accepted for publication in Solar Physics

References in corpus (4)

• Formation of Relativistic Outflows in Shearing Black Hole Accretion Coronae
• Acceleration of energetic particles by large-scale compressible magnetohydrodynamic turbulence
• Exact solution for the Green's function describing time-dependent thermal Comptonization
• Spectrum of Solar Type I Continuum Noise Storm in the 50 - 80 MHz band, and Plasma characteristics in the associated source region

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• Electron acceleration in a post-flare decimetric continuum source
• Further constraints on electron acceleration in solar noise storms
• Radio, X-ray and extreme-ultraviolet observations of weak energy releases in the `quiet' Sun