论文标题
月球流体核心中的粘性耗散
Viscous dissipation in the fluid core of the Moon
论文作者
论文摘要
尽管有不同的方向，但月球序列的旋转轴，流体核心和固体内核的频率$ω_p=2π/18.6 $ yr $^{ - 1} $，导致核心棒球边界（CMB）和内核边界（ICB）的粘性摩擦。在这里，我们使用具有一系列内核和外部核心半径的月球旋转模型来研究CMB和ICB粘性耗散的相对重要性，并展示了这种耗散是如何连接到其cassini州前面壁板的相位铅角（$ ϕ_P $）的相对重要性。我们表明，当内部核心半径为$> 80 $ km，并且自由的内核营养频率$ω__{ficn} $接近$ω_p$，ICB处的粘性散发与CMB可以媲美，并且在最极端的情况下，它超过了它的范围10。 $ω__{ficn} $相对于$ω_p$演变。我们进一步表明，可以通过匹配$ ϕ_p = 0.27 $ arcsec的观察到的相位铅来提取对月芯的CMB和ICB半径的约束；这需要改善潮汐耗散的估计值和湍流粘性扭矩的准确模型。最后，当我们的旋转模型被限制为匹配$ ϕ_p = 0.27 $ arcsec时，我们的结果表明，ICB处的粘性耗散可能不足以超过阈值，无法为热驱动的发电机供电。
The spin axes of the mantle, fluid core and solid inner core of the Moon precess at frequency $Ω_p=2π/18.6$ yr$^{-1}$ though with different orientations, leading to viscous friction at the core-mantle boundary (CMB) and inner core boundary (ICB). Here, we use a rotational model of the Moon with a range of inner core and outer core radii to investigate the relative importance of viscous dissipation at the CMB and ICB, and to show how this dissipation is connected to the phase lead angle ($ϕ_p$) of the mantle ahead of its Cassini state. We show that when the inner core radius is $>80$ km and the free inner core nutation frequency $Ω_{ficn}$ approaches $Ω_p$, viscous dissipation at the ICB can be comparable to that at the CMB, and in the most extreme cases exceed it by as much as a factor 10. If so, the viscous dissipation in the lunar core projected back in time depends on how $Ω_{ficn}$ has evolved relative to $Ω_p$. We further show that constraints on the CMB and ICB radii of the lunar core can in principle be extracted by matching the observed phase lead of $ϕ_p=0.27$ arcsec; this requires an improved estimate of tidal dissipation and an accurate model of the turbulent viscous torque. Lastly, when our rotational model is constrained to match $ϕ_p=0.27$ arcsec, our results suggest that the viscous dissipation at the ICB is likely insufficient to have ever been above the threshold to power a thermally driven dynamo.
