Abstract
We consider the evolution of lithium in the solar convective zone to explain its low content. The burning of lithium in a nuclear reaction 7Li(p,α)4He occurs intensely at an early stage from the moment of radiative core formation, and its content slowly decreases on the main sequence (MS). We study the percentage of lithium depletion at these two stages. The model without additional mixing below a convective zone predicts a sevenfold decrease of the lithium content, which is considerably less than that required by the observations (160-fold decrease). The new results of the helioseismic inversion indicate on existence of an overshooting region below the convective zone, the thickness of which cannot exceed 3.8% of the solar radius and is likely even thinner. The inclusion of this region in the evolution calculations indicates that lithium cannot burn out in a sufficient quantity on the MS stage. We conclude that lithium must be depleted at an early stage of evolution before the MS. At this early stage, even a relatively small overshooting in the region with a thickness of about 18% of the pressure scale height is sufficient to decrease the lithium content to the observed value.
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Oreshina, A.V., Baturin, V.A. & Gorshkov, A.B. The role of mixing below the convective zone in evolution of solar lithium. Geomagn. Aeron. 55, 1171–1174 (2015). https://doi.org/10.1134/S0016793215080241
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DOI: https://doi.org/10.1134/S0016793215080241