In a study published in The Astrophysical Journal, ZHANG Qiansheng and LI Yan from Yunnan Observatories of the Chinese Academy of Sciences and Christensen-Dalsgaard Joergen from Aarhus University, Denmark, investigated the effects of convective overshoot, solar wind, and pre-main-sequence (PMS) accretion on solar models, and found a solution to the long-standing "solar abundance problem".
The "solar abundance problem" is that some properties (the depth and helium abundance of the convection zone, sound speed and density profiles in solar interior, and the surface lithium abundance) of the current standard solar model are not consistent with observations. The problem has arisen from 2004 and lasts for more than a decade.
By analyzing the inconsistences of the standard solar model and overall considerations, the scientists proposed to take into account convective overshoot, the solar wind, and PMS accretion in stellar evolution.
They derived mathematical models for those physical processes and calculated solar models with different parameters.
The results showed that when the PMS accretion is helium-poor, there are solar models consistent with all observations. A typical improved solar model is the Model TWA. Its properties (the depth and helium abundance of the convection zone, the surface lithium abundance, sound speed and density profiles, and neutrino fluxes) are overall consistent with observations.
This study revealed the significant effects of some physical processes ignored in standard theory of stellar evolution. It pointed out for the first time that the solar wind is necessary to model the Sun and that PMS accretion could be inhomogeneous.
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