Atomic Data and Solar Photospheric Spectroscopy

Solar Chemical Abundances Determined with a CO5BOLD 3D Model Atmosphere

In the last decade, the photospheric solar metallicity as determined from spectroscopy experienced a remarkable downward revision. Part of this effect can be attributed to an improvement of atomic data and the inclusion of NLTE computations, but also the use of hydrodynamical model atmospheres seemed to play a role. This “decrease” with time of the metallicity of the solar photosphere increased...

Segmentation of Photospheric Solar Images by Using c-Means,k-Means, and FCM Algorithms

IMPROVED ATOMIC DATA FOR HO ii AND NEW HOLMIUM ABUNDANCES FOR THE SUN AND THREE METAL-POOR STARS

Improved energy levels and hyperfine structure constants for a selected set of Ho ii levels were measured from spectra recorded Q1 using the 1 m Fourier transform spectrometer (FTS) at the US National Solar Observatory. Branching fractions for the strong blue-UV lines from these levels were also measured from the FTS data and combined with earlier radiative lifetimes from time-resolved laser-in...

IMPROVED LABORATORY TRANSITION PROBABILITIES FOR Gd ii AND APPLICATION TO THE GADOLINIUM ABUNDANCES OF THE SUN AND THREE r-PROCESS RICH, METAL-POOR STARS

Radiative lifetimes, accurate to 5%, have been measured for 49 even-parity and 14 odd-parity levels of Gd ii using laser-induced fluorescence. The lifetimes are combined with branching fractions measured using Fourier transform spectrometry to determine transition probabilities for 611 lines of Gd ii. Thiswork is the largest-scale laboratory study to date of Gd ii transition probabilities and t...

The Hanle Effect in Atomic and Molecular Lines: A New Look at the Sun’s Hidden Magnetism

This paper reviews some of the most recent advances in the application of the Hanle effect to solar physics, and how these developments are allowing us to explore the magnetism of the photospheric regions that look “empty” in solar magnetograms—that is, the Sun’s “hidden” magnetism. In particular, we show how a joint analysis of the Hanle effect in atomic and molecular lines indicates that ther...