On the relationship between zonal jets and dynamo action in giant planets
On the relationship between zonal jets and dynamo action in giant planets
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巨行星中纬向喷流与发电机作用之间的关系
DOI：
10.1029/2011gl047562
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发表时间：
2011
影响因子：
5.2
通讯作者：
Natalia Gómez Pérez
中科院分区：
文献类型：
--
作者：
M. Heimpel;Natalia Gómez Pérez
木星和土星表现出类似的大尺度动力学特征。每颗行星都有一个顺行的赤道喷流和一个深层的偶极磁场。与木星相比，土星的喷流更宽、速度更快，而其磁场更弱、轴对称性更强。太阳还具有顺行的赤道流和大范围的轴向磁场。虽然太阳差异自转的深度受到日震学的很好限制，但纬向风穿透巨行星的深度尚不清楚，并且一直是争论的话题。尽管磁制动已被用作减慢深度风速的机制，但这种机制此前尚未得到证实。在这里，我们提出了第一个自洽数值行星发电机模型，其中内部发电机源区域的慢对流与外表面附近的强纬向流共存。这些模型包括径向可变的电导率，并表明顺行纬向流渗透到洛伦兹力平衡雷诺应力的深度，雷诺应力驱动赤道急流。我们的结果表明，木星和土星表面纬向流之间的主要差异源于类似于太阳速斜层的过渡层的不同深度和条件。这个过渡层，即行星速跃层，将高速的半导体分子包膜与缓慢移动的液态金属内部发电机分开。
Jupiter and Saturn exhibit similar large‐scale dynamical features. Each planet has a prograde equatorial jet and a deeply seated dipolar magnetic field. Compared to Jupiter, Saturn's jet is broader and faster, while its magnetic field is weaker and more axially symmetric. The Sun also has prograde equatorial flow and a large‐scale axial magnetic field. While the depth of the Sun's differential rotation is well constrained by helioseismology, the depth to which the zonal winds penetrate in the giant planets is not known and has been a subject of debate. Although magnetic braking has been invoked as the mechanism to slow the winds at depth, such a mechanism has not previously been demonstrated. Here we present the first self‐consistent numerical planetary dynamo models in which slow convection in the interior dynamo source region coexists with strong zonal flow near the outer surface. The models include radially variable electrical conductivity and show that prograde zonal flow penetrates to a depth where Lorentz forces balance the Reynolds stress, which drives the equatorial jet. Our results imply that major differences between the surface zonal flows of Jupiter and Saturn arise from the different depths and conditions of a transition layer analogous to the solar tachocline. This transition layer, the planetary tachocline, separates the high velocity, semiconducting molecular envelope from the slow moving liquid metal interior dynamo.