标题： 在木星内部存在倒置Z梯度的假设下 显示英文标题

标题： On the hypothesis of an inverted Z-gradient inside Jupiter

摘要： 木星内部模型难以与大气成分的测量结果达成一致。内部模型倾向于支持重元素Z的太阳或次太阳丰度，而大气测量则表明其具有超太阳丰度。一种可能的解决方案可能是存在一个倒置的Z梯度，即Z的内向减少，这意味着大气中的重元素丰度高于外层包层。我们研究了两种情景，其中倒置的Z梯度分别位于氦雨发生的地方（兆巴级）或上层（千巴级），在该处可能存在一个辐射区。我们的目标是评估这些情景的合理性。我们计算了具有这种倒置Z梯度的木星内部和演化模型，并使用稳定性约束和倒置Z梯度形成条件。我们发现，在氦雨发生位置的倒置Z梯度无法成立，因为它需要较晚的吸积且吸收的物质过多。我们发现在上层存在倒置Z梯度的内部模型，由于辐射区阻止了向下混合，这可能满足行星当前的引力场。然而，我们的演化模型表明，第二种情景可能并不成立。木星中存在一个倒置的Z梯度可能是稳定的。但是，无论是位于兆巴级还是千巴级，它的存在都是不太可能的。 显示英文摘要

摘要： Models of Jupiter s interior struggle to agree with measurements of the atmospheric composition. Interior models favour a subsolar or solar abundance of heavy elements Z while atmospheric measurements suggest a supersolar abundance. One potential solution may be the presence of an inverted Z-gradient, namely an inward decrease of Z, which implies a larger heavy element abundance in the atmosphere than in the outer envelope. We investigate two scenarios in which the inverted Z gradient is located either where helium rain occurs (Mbar level) or at upper levels (kbar level) where a radiative region could exist. We aim to assess how plausible these scenarios are. We calculate interior and evolution models of Jupiter with such inverted Z-gradient and use constraints on the stability and the formation of an inverted Z-gradient. We find that an inverted Z-gradient at the location of helium rain cannot work as it requires a late accretion and of too much material. We find interior models with an inverted Z-gradient at upper levels, due to a radiative zone preventing downward mixing, that could satisfy the present gravity field of the planet. However, our evolution models suggest that this second scenario might not be in place. An inverted Z-gradient in Jupiter could be stable. Yet, its presence either at the Mbar level or kbar level is rather unlikely.