Atomic Physics at the Extreme: The Solar Abundance Problem

A special issue of Atoms (ISSN 2218-2004).

Deadline for manuscript submissions: closed (15 January 2020) | Viewed by 3859

Special Issue Editor


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Guest Editor
Racah Institute of Physics and The Hebrew University of Jerusalem, Jerusalem, Israel
Interests: many body quantum systems; nuclei and atoms in stars; atoms in hot and dense matter

Special Issue Information

Dear Colleagues,

Over the past decade, a new solar problem has emerged, as solar photospheric abundances have been improved and the indicated solar metallicity, which is mainly due to low-Z metallic elements, has been significantly revised downward from that previously assumed. Standard solar models do not reproduce helioseismic observables when using these revised abundances. This has given rise to the solar composition problem. The amount of metals directly modifies the opacity profile of the Sun, and the solar composition problem is strongly related to the role of opacity in solar models. This has motivated a plethora of new studies, both experimental and theoretical, to understand atomic physics in the extreme environment of the Sun.

It is understood that the opacity of metals in the stellar mixture should be revised upward to compensate for the decreased abundances of low-Z metallic elements. Theoretically, it was found that details of the distribution of electrons and ions, which are highly uncertain, significantly affect the resulting opacity. In addition, the monochromatic opacity of iron, a major contributor to solar opacity, was recently measured in very similar conditions to those expected near the boundary of the solar convection zone. The measured spectrum appears to be larger than those calculated through various state-of-the-art and widely used atomic models by about a factor of two in several spectral regions near the L-shell photoabsorption lines. Moreover, measurements in neighbor elements at similar conditions, as well as in iron at different temperatures, do not show this effect. No satisfactory explanation for these observations has been provided.

This Special Issue of Atoms will highlight the need for continuing research on the different atomic properties affecting heat transport in the Sun as well as other main sequence stars and astrophysical phenomena. In addition, the importance of laboratory studies of hot and dense plasmas will be discussed. Particular emphasis will be put on new directions to study opacities in solar conditions and their relation to the solar abundance problem.

Prof. Dr. Doron Gazit
Guest Editor

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Keywords

  • Solar Physics
  • Main sequence stars
  • opacity
  • hot and dense matter
  • laboratory plasma
  • line shapes
  • Z-machine
  • high energy density physics

Published Papers (1 paper)

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Review

16 pages, 3153 KiB  
Review
Element Abundances of Solar Energetic Particles and the Photosphere, the Corona, and the Solar Wind
by Donald V. Reames
Atoms 2019, 7(4), 104; https://doi.org/10.3390/atoms7040104 - 20 Nov 2019
Cited by 7 | Viewed by 3462
Abstract
From a turbulent history, the study of the abundances of elements in solar energetic particles (SEPs) has grown into an extensive field that probes the solar corona and physical processes of SEP acceleration and transport. Underlying SEPs are the abundances of the solar [...] Read more.
From a turbulent history, the study of the abundances of elements in solar energetic particles (SEPs) has grown into an extensive field that probes the solar corona and physical processes of SEP acceleration and transport. Underlying SEPs are the abundances of the solar corona, which differ from photospheric abundances as a function of the first ionization potentials (FIPs) of the elements. The FIP-dependence of SEPs also differs from that of the solar wind; each has a different magnetic environment, where low-FIP ions and high-FIP neutral atoms rise toward the corona. Two major sources generate SEPs: The small “impulsive” SEP events are associated with magnetic reconnection in solar jets that produce 1000-fold enhancements from H to Pb as a function of mass-to-charge ratio A/Q, and also 1000-fold enhancements in 3He/4He that are produced by resonant wave-particle interactions. In large “gradual” events, SEPs are accelerated at shock waves that are driven out from the Sun by wide, fast coronal mass ejections (CMEs). A/Q dependence of ion transport allows us to estimate Q and hence the source plasma temperature T. Weaker shock waves favor the reacceleration of suprathermal ions accumulated from earlier impulsive SEP events, along with protons from the ambient plasma. In strong shocks, the ambient plasma dominates. Ions from impulsive sources have T ≈ 3 MK; those from ambient coronal plasma have T = 1 – 2 MK. These FIP- and A/Q-dependences explore complex new interactions in the corona and in SEP sources. Full article
(This article belongs to the Special Issue Atomic Physics at the Extreme: The Solar Abundance Problem)
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