Effects of the Electron Energy Distribution Function on Line and Continuum Emission

Abstract

Effects of suprathermal (“hot”) electrons on the predictions of K‐ and L‐shell non‐LTE collisional‐radiative atomic kinetics models are presented through an investigation of various electron distribution functions (EDFs) on collisional rates and spectra. It is shown that while most collisional rates are fairly insensitive to the functional form and characteristic energy of the hot electrons as long as their characteristic energy is larger than the threshold energy for the collisional process, collisional excitation and ionization rates are highly sensitive to the fraction of hot electrons. This permits the development of robust spectroscopic diagnostics that can be used to detect the presence of hot electrons from x‐ray line emission spectra. Hot electrons are shown to increase and spread out plasma charge state distributions, amplify the intensities of emission lines fed by direct collisional excitation and radiative cascades, and alter the structure of satellite and EUV line emission features. The characteristic energy, functional form, and spatial properties of hot electron distributions in plasmas are open to characterization through their effects on high‐energy continuum emission and on the polarization of spectral lines.