Combined magnetic and gravity measurements probe the deep zonal flows of the gas giants
Combined magnetic and gravity measurements probe the deep zonal flows of the gas giants
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结合磁力和重力测量来探测气态巨行星的深层纬向流
DOI：
10.1093/mnras/staa3722
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发表时间：
2020
影响因子：
4.8
通讯作者：
Y. Kaspi
中科院分区：
文献类型：
--
作者：
E. Galanti;Y. Kaspi
<p>朱诺号和卡西尼号的重力测量表明，在气态巨行星的云层中观察到的强烈的纬向流延伸到数千公里深的行星内部。然而，单独的重力测量，这是一个综合的质量测量的定义，不能约束与高度的确定性，详细的垂直结构的流低于云的水平。在这里，我们表明，考虑到最近的磁场测量的土星和过去的长期变化的木星的磁场，给一个额外的物理约束的垂直衰减剖面上观察到的纬向流在这些行星。在土星，我们发现云层风延伸到行星，几乎没有衰减（正压），直到大约7,000公里的深度，然后迅速衰减，因此在接下来的1,000公里内，它们的值减少到云层的1%左右。土星的这种最佳深流剖面结构同时与重力场和最近测量发现的磁场高阶纬向变化相匹配。在木星的情况下，使用最近的研究结果表明，在行星半导体区域的流量是每秒厘米级，我们表明，有这样的约束，一个类似于土星的流动结构是一致的朱诺重力测量。在这里，风从云层一直延伸到大约2,000公里的深度，然后在接下来的600公里内迅速衰减到大约1%的值。因此，在这两颗巨行星上，我们发现观测到的风都没有改变（正压），一直延伸到半导体区，然后突然衰减。虽然在半导体区域与磁场的相互作用是导致风最终衰变的原因，但还不清楚是否有其他机制参与这个过程，特别是在10秒每秒的强风的初始衰变中。</p>
<p>The strong zonal flows observed at the cloud-level of the gas giants extend thousands of kilometers deep into the planetary interior, as indicated by the Juno and Cassini gravity measurements. However, the gravity measurements alone, which are by definition an integrative measure of mass, cannot constrain with high certainty the detailed vertical structure of the flow below the cloud-level. Here we show that taking into account the recent magnetic field measurements of Saturn and past secular variations of Jupiter's magnetic field, give an additional physical constraint on the vertical decay profile of the observed zonal flows in these planets. In Saturn, we find that the cloud-level winds extend into the planet with very little decay (barotropically) down to a depth of around 7,000 km, and then decay rapidly, so that within the next 1,000 km their value reduces to about 1% of that at the cloud-level. This optimal deep flow profile structure of Saturn matches simultaneously both the gravity field and the high-order latitudinal variations in the magnetic field discovered by the recent measurements. In the Jupiter case, using the recent findings indicating the flows in the planet semiconducting region are order centimeters per second, we show that with such a constraint, a flow structure similar to the Saturnian one is consistent with the Juno gravity measurements. Here the winds extend unaltered from the cloud-level to a depth of around 2,000 km and then decay rapidly within the next 600 km to values of around 1%. Thus, in both giant planets, we find that the observed winds  extend unaltered (baroctropically) down to the semiconducting region, and then decay abruptly. While it is plausible that the interaction with the magnetic field in the semiconducting region is responsible for winds final decay, it is yet to be understood whether another mechanism is involved in the process, especially in the initial decay form the strong 10s meter per seconds winds.</p>
影响因子：
8.7
作者：
French, Martin;Becker, Andreas;Redmer, Ronald
通讯作者：
Redmer, Ronald
影响因子：
3.2
作者：
Gastine, T.;Wicht, J.
通讯作者：
Wicht, J.