Thermal Doppler Broadening of Spectral Emissions in Space and Astrophysical Plasmas

The paper develops analytical modeling of thermal Doppler broadening of spectral profiles for particle populations described by kappa distributions, in the absence or presence of potential fields. The kappa distribution provides a straightforward replacement for the Maxwell distribution, that is, a generalization for describing systems characterized by local correlations among their particles, commonly found in space and astrophysical plasmas. The corresponding Voigt profiles are derived by convoluting the thermal and natural/collisional Lorentzian profiles. The kappa velocity distributions are employed to derive the thermal Doppler and Voigt profiles, while the kappa phase-space distributions in the presence of potential fields that depend on the position vector, are used to derive their respective differential profiles. We focus on attractive power-law potentials (oscillation-type, gravitational-type, and angular potentials), and study the variations of the produced Voigt differential profiles in detail. The developed formulations and guidelines provide a useful and statistically well-grounded "toolbox" for future reference in data analyses, simulations, analytical modeling, and theories of spectroscopy and related subjects of space and astrophysical plasmas.