Stark-Zeeman Line Shape Modeling for Magnetic White Dwarf and Tokamak Edge Plasmas: Common Challenges

Abstract

Abstract:The shape of atomic spectral lines in plasmas contains information on the plasma parameters, and can be used as a diagnostic tool. Under specific conditions, the plasma located at the edge of tokamaks has parameters similar to those in magnetic white dwarf stellar atmospheres, which suggests that the same line shape models can be used. A problem common to tokamak and magnetic white dwarfs concerns the modeling of Stark broadening of hydrogen lines in the presence of an external magnetic field and the related Zeeman effect. In this work, we focus on a selection of issues relevant to Stark broadening in magnetized hydrogen plasmas. Various line shape models are presented and discussed through applications to ideal cases.

Laboratory Hydrogen-Beta Emission Spectroscopy for Analysis of Astrophysical White Dwarf Spectra

“…For H α and H β , the Zeeman-splits amount to an energy shift 0.038 eV on each side of line center. The shifts in Figure 5 imply magnetic fields of the order of 500 Tesla, also indicated in the computed H α Zeeman triplet [61] for a magnetic field of 500 Tesla. The electron density estimate equals 3.1 × 10 17 cm −3 , determined from FWHM of the central absorption of H β , ∆w Hβ = 10 ± 1 nm, and H α , ∆w Hα = 2.7 ± 0.5 nm.…”

“…As an example of a magnetic DA type star (DAH), the Zeeman triplets are nicely recognizable in Figure 5. Magnetic white dwarfs pose challenges [61,62] in the modeling of the recorded absorption spectra. The H β and H α profiles in Figure 5 indicate Zeeman-split blue-and red-peak separations, respectively, of σ β = 14.6 nm and σ α = 26.6 nm.…”

Laboratory Hydrogen-Beta Emission Spectroscopy for Analysis of Astrophysical White Dwarf Spectra

“…5. Magnetic white dwarfs pose challenges [58] in the modeling of the recorded absorption spectra. The H β and H α profiles in Fig.…”

A New Analysis of Stark and Zeeman Effects on Hydrogen Lines in Magnetized DA White Dwarfs

“…The ion dynamics leads to an additional broadening, which can be important especially at low densities, high temperatures, or for lines with a low upper principal quantum number. Simulations involving a numerical integration of the Liouville Equation (3) and not referring to Equation (5) can also be performed, but they become time-consuming if the atomic system is complex [7,14,15].…”

“…The design of a line shape model accounting for both Stark broadening and Zeeman splitting is not straightforward, because these two effects do not act as additive perturbations. Previous investigations in low-density (tokamak edge) magnetized plasma conditions have indicated an alteration of the broadening of each Zeeman component due to the change of the atomic energy level structure (degeneracy removal) in response to an external magnetic field [7,8]. This issue also concerns magnetized white dwarfs with spectra exhibiting Zeeman splitting.…”