Importance of Angle-dependent Partial Frequency Redistribution in Hyperfine Structure Transitions Under Incomplete Paschen-Back Effect Regime

Abstract

Angle-frequency coupling in scattering of polarized light on atoms is represented by the angle-dependent (AD) partial frequency redistribution (PRD) matrices. There are several lines in the linearly polarized solar spectrum, for which PRD combined with quantum interference between hyperfine structure states play a significant role. Here we present the solution of the polarized line transfer equation including the AD-PRD matrix for scattering on a two-level atom with hyperfine structure splitting (HFS) and an unpolarized lower level. We account for the effects of arbitrary magnetic fields (including the incomplete Paschen-Back effect regime) and elastic collisions. For exploratory purposes we consider a self-emitting isothermal planar atmosphere and use atomic parameters that represent an isolated Na\,{\sc i} D${}_2$ line. For this case we show that the AD-PRD effects are significant for field strengths below about 30G, but that the computationally much less demanding approximation of angle-averaged (AA) PRD may be used for stronger fields.

15 pages, 9 figures, Accepted for publication in the Astrophysical Journal

References in corpus (7)

• Magnetic Diagnostics of the Solar Chromosphere with the Mg II h-k Lines
• The magnetic sensitivity of the Mg ii k line to the joint action of Hanle, Zeeman and magneto-optical effects
• The magnetic sensitivity of the resonance and subordinate lines of Mg II in the solar chromosphere
• The transfer of resonance line polarization with partial frequency redistribution in the general Hanle-Zeeman regime
• Master equation theory applied to the redistribution of polarized radiation in the weak radiation field limit. V. The two-term atom
• An efficient decomposition technique to solve angle-dependent Hanle scattering problems
• Polarized Line Formation in Arbitrary Strength Magnetic Fields: the case of a two-level atom with hyperfine structure splitting