Abstract

We provide an approximate formula for the calculation of second-order moments of pressure-broadened hydrogen lines in the quasi-static approximation. Our derivation is based on the results of previous investigations of the algebraic second-order moments of polarized hydrogen lines in the presence... Show moreWe provide an approximate formula for the calculation of second-order moments of pressure-broadened hydrogen lines in the quasi-static approximation. Our derivation is based on the results of previous investigations of the algebraic second-order moments of polarized hydrogen lines in the presence of Stark broadening mechanisms. The approximation involved consists in considering a limited spectral range for the estimate of the second-order moment of the line profile. The problem of the formal divergence of the second-order moments of pressure-broadened hydrogen lines because of the infinite contribution from the wings is so avoided. The approximation we present seems to be robust enough for setting up a very direct diagnostics of charged perturber density in low-density plasmas, like solar prominences, based on the analysis of hydrogen line widths, if the conditions for a quasi-static treatment of pressure broadening are sufficiently well verified. Show less