ترغب بنشر مسار تعليمي؟ اضغط هنا

On the solar abundance of indium

389   0   0.0 ( 0 )
 نشر من قبل Nikola Vitas
 تاريخ النشر 2007
  مجال البحث فيزياء
والبحث باللغة English




اسأل ChatGPT حول البحث

The generally adopted value for the solar abundance of indium is over six times higher than the meteoritic value. We address this discrepancy through numerical synthesis of the 451.13 nm line on which all indium abundance studies are based, both for the quiet-sun and the sunspot umbra spectrum, employing standard atmosphere models and accounting for hyperfine structure and Zeeman splitting in detail. The results, as well as a re-appraisal of indium nucleosynthesis, suggest that the solar indium abundance is close to the meteoritic value, and that some unidentified ion line causes the 451.13 nm feature in the quiet-sun spectrum.

قيم البحث

اقرأ أيضاً

Motivated by the controversy over the surface metallicity of the Sun, we present a re-analysis of the solar photospheric oxygen (O) abundance. New atomic models of O and Ni are used to perform Non-Local Thermodynamic Equilibrium (NLTE) calculations w ith 1D hydrostatic (MARCS) and 3D hydrodynamical (Stagger and Bifrost) models. The Bifrost 3D MHD simulations are used to quantify the influence of the chromosphere. We compare the 3D NLTE line profiles with new high-resolution, R = 700 000, spatially-resolved spectra of the Sun obtained using the IAG FTS instrument. We find that the O I lines at 777 nm yield the abundance of log A(O) = 8.74 +/- 0.03 dex, which depends on the choice of the H-impact collisional data and oscillator strengths. The forbidden [O I] line at 630 nm is less model-dependent, as it forms nearly in LTE and is only weakly sensitive to convection. However, the oscillator strength for this transition is more uncertain than for the 777 nm lines. Modelled in 3D NLTE with the Ni I blend, the 630 nm line yields an abundance of log A(O) = 8.77 +/- 0.05 dex. We compare our results with previous estimates in the literature and draw a conclusion on the most likely value of the solar photospheric O abundance, which we estimate at log A(O) = 8.75 +/- 0.03 dex.
The abundance of iron is measured from emission line complexes at 6.65 keV (Fe line) and 8 keV (Fe/Ni line) in {em RHESSI} X-ray spectra during solar flares. Spectra during long-duration flares with steady declines were selected, with an isothermal a ssumption and improved data analysis methods over previous work. Two spectral fitting models give comparable results, viz. an iron abundance that is lower than previous coronal values but higher than photospheric values. In the preferred method, the estimated Fe abundance is $A({rm Fe}) = 7.91 pm 0.10$ (on a logarithmic scale, with $A({rm H}) = 12$), or $2.6 pm 0.6$ times the photospheric Fe abundance. Our estimate is based on a detailed analysis of 1,898 spectra taken during 20 flares. No variation from flare to flare is indicated. This argues for a fractionation mechanism similar to quiet-Sun plasma. The new value of $A({rm Fe})$ has important implications for radiation loss curves, which are estimated.
We present the result of our investigation on the impact of the low Solar abundance of Asplund and collaborators (2004) on the derived ages for the oldest star clusters based on isochrone fittings. We have constructed new stellar models and correspon ding isochrones using this new solar mixture with a proper Solar calibration. We have found that the use of the Asplund et al. (2004) metallicity causes the typical ages for old globular clusters in the Milky Way to be increased roughly by 10%. Although this may appear small, it has a significant impact on the interpretation for the formation epoch of Milky Way globular clusters. The Asplund et al. (2004) abundance may not necessarily threaten the current concordance cosmology but would suggest that Milky Way globular clusters formed before the reionization and before the main galaxy body starts to build up. This is in contrast to the current understanding on the galaxy formation.
We discuss the level of agreement of a new generation of standard solar models (SSMs), Barcelona 2016 or B16 for short, with helioseismic and solar neutrino data, confirming that models implementing the AGSS09met surface abundances, based on refined three-dimensional hydrodynamical simulations of the solar atmosphere, do not not reproduce helioseismic constraints. We clarify that this solar abundance problem can be equally solved by a change of the composition and/or of the opacity of the solar plasma, since effects produced by variations of metal abundances are equivalent to those produced by suitable modifications of the solar opacity profile. We discuss the importance of neutrinos produced in the CNO cycle for removing the composition-opacity degeneracy and the perspectives for their future detection.
We study the solar wind helium-to-hydrogen abundances ($A_mathrm{He}$) relationship to solar cycle onset. Using OMNI/Lo data, we show that $A_mathrm{He}$ increases prior to sunspot number (SSN) minima. We also identify a rapid depletion and recovery in $A_mathrm{He}$ that occurs directly prior to cycle onset. This $A_mathrm{He}$ Shutoff happens at approximately the same time across solar wind speeds ($v_mathrm{sw}$), implying that it is formed by a mechanism distinct from the one that drives $A_mathrm{He}$s solar cycle scale variation and $v_mathrm{sw}$-dependent phase offset with respect to SSN. The time between successive $A_mathrm{He}$ shutoffs is typically on the order of the corresponding solar cycle length. Using Brightpoint (BP) measurements to provide context, we infer that this shutoff is likely related to the overlap of adjacent solar cycles and the equatorial flux cancelation of the older, extended solar cycle during Solar Minima.
التعليقات
جاري جلب التعليقات جاري جلب التعليقات
سجل دخول لتتمكن من متابعة معايير البحث التي قمت باختيارها
mircosoft-partner

هل ترغب بارسال اشعارات عن اخر التحديثات في شمرا-اكاديميا