Linking zonal winds and gravity – II. Explaining the equatorially antisymmetric gravity moments of Jupiter
Linking zonal winds and gravity – II. Explaining the equatorially antisymmetric gravity moments of Jupiter
复制标题
连接纬向风和重力 - II 解释木星的赤道反对称重力矩
DOI：
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发表时间：
2021
期刊：
影响因子：
--
通讯作者：
U. Christensen
中科院分区：
文献类型：
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作者：
W. Dietrich;P. Wulff;J. Wicht;U. Christensen
最近对木星(朱诺星)和土星(卡西尼号)的重力场测量证实，存在深达各自半径5%和15%深度的纬向流。将纬向风引起的密度扰动与引力矩联系起来，已成为描述气态巨星内部动力学的主要工具。以往的研究在风速如何与密度异常相关、风速随深度衰减的函数形式以及赤道平面上反对称风的连续性的假设方面存在差异。大多数垂直结构显示出相当平稳的纬向风的径向衰减，这似乎与观测到的磁场的长期变化和纬向风的普遍地转相抵触。此外，结果依赖于人为的赤道正则化或完全忽略了赤道不连续。我们倾向于另一种结构，在这种结构中，赤道纬度带上±21◦之间的赤道反对称纬向风仍然很浅，因此它对重力信号没有贡献。高纬度的风足以令人信服地解释测量到的重力矩。我们的结果表明，风是地转的，即沿着柱面不变，在3000公里外，风在下方迅速减弱。优选的风结构比以前认为的要深50%，与测量的重力矩一致，符合磁力约束和绝热大气的要求，并且不受赤道不连续处理的影响。
The recent gravity field measurements of Jupiter (Juno) and Saturn (Cassini) confirm the existence of deep zonal flows reaching to a depth of 5% and 15% of the respective radius. Relating the zonal wind induced density perturbations to the gravity moments has become a major tool to characterise the interior dynamics of gas giants. Previous studies differ with respect to the assumptions made on how the wind velocity relates to density anomalies, on the functional form of its decay with depth, and on the continuity of antisymmetric winds across the equatorial plane. Most of the suggested vertical structures exhibit a rather smooth radial decay of the zonal wind, which seems at odds with the observed secular variation of the magnetic field and the prevailing geostrophy of the zonal winds. Moreover, the results relied on an artificial equatorial regularisation or ignored the equatorial discontinuity altogether. We favour an alternative structure, where the equatorially antisymmetric zonal wind in an equatorial latitude belt between ±21◦ remains so shallow that it does not contribute to the gravity signal. The winds at higher latitudes suffice to convincingly explain the measured gravity moments. Our results indicate that the winds are geostrophic, i.e. constant along cylinders, in the outer 3000 km and decay rapidly below. The preferred wind structure is 50% deeper than previously thought, agrees with the measured gravity moment, is compliant with the magnetic constraints and the requirement of an adiabatic atmosphere and unbiased by the treatment of the equatorial discontinuity.
影响因子：
8.7
作者：
French, Martin;Becker, Andreas;Redmer, Ronald
通讯作者：
Redmer, Ronald
影响因子：
4.9
作者：
Nettelmann, N.;Becker, A.;Redmer, R.
通讯作者：
Redmer, R.
影响因子：
3.2
作者：
Gastine, T.;Wicht, J.
通讯作者：
Wicht, J.