New Solar Metallicity Measurements

Sunny Vagnozzi

doi:10.3390/atoms7020041

Abstract

In the past years, a systematic downward revision of the metallicity of the Sun has led to the “solar modeling problem”, namely the disagreement between predictions of standard solar models and inferences from helioseismology. Recent solar wind measurements of the metallicity of the Sun, however, provide once more an indication of a high-metallicity Sun. Because of the effects of possible residual fractionation, the derived value of the metallicity Z ⊙ = 0 . 0196 ± 0 . 0014 actually represents a lower limit to the true metallicity of the Sun. However, when compared with helioseismological measurements, solar models computed using these new abundances fail to restore agreement, owing to the implausibly high abundance of refractory (Mg, Si, S, Fe) elements, which correlates with a higher core temperature and hence an overproduction of solar neutrinos. Moreover, the robustness of these measurements is challenged by possible first ionization potential fractionation processes. I will discuss these solar wind measurements, which leave the “solar modeling problem” unsolved.

Highlights

The “Solar Modeling Problem”The metallicity of the Sun, Z , i.e., the fraction of solar mass residing in elements heavier than helium, is a fundamental diagnostic of the evolutionary history of our star
The Oskar Klein Centre for Cosmoparticle Physics, Department of Physics, Stockholm University, AlbaNova Universitetscentrum, Roslagstullsbacken 21A, SE-106 91 Stockholm, Sweden; The Nordic Institute for Theoretical Physics (NORDITA), Roslagstullsbacken 23, SE-106 91 Stockholm, Sweden
As for the surface helium abundance, as per expectations due to the increase in the abundance of refractories, we find that this quantity increases well beyond the values allowed by helioseismology, worsening the AGSS09 disagreement

Summary

The “Solar Modeling Problem”

The metallicity of the Sun, Z , i.e., the fraction of solar mass residing in elements heavier than helium, is a fundamental diagnostic of the evolutionary history of our star. The sets of abundances known as AGS05 [3] and AGSS09 [4] report a metallicity of Z = 0.0122 and Z = 0.0133, respectively These revisions have completely spoiled the previous agreement between models and helioseismology, leading to what is known as the “solar modeling problem” (see, e.g., [5] for a review). I will consider another possibility, namely that the solar metallicity determined using spectroscopic methods might not be representative of the true metallicity of the Sun. I will consider alternative measurements from solar wind emerging from polar coronal holes, previously reported in [17]. I briefly reassess these findings and provide a summary of the current status of solar models in light of solar wind measurements. 1

In Situ Solar Wind Measurements of Metallicity

New Measurements: vSZ16

Implications for the “Solar Modeling Problem”

Solar Wind Systematics

Findings

Conclusions