Magnetic damping of jet flows in quasi-two-dimensional Rayleigh-Bénard convection
Magnetic damping of jet flows in quasi-two-dimensional Rayleigh-Bénard convection
复制标题
准二维瑞利-贝纳德对流射流的磁阻尼
DOI：
10.1103/physreve.106.045104
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发表时间：
2022
影响因子：
2.4
通讯作者：
Horn, Susanne
中科院分区：
文献类型：
--
作者：
Aggarwal, Ashna;Aurnou, Jonathan M.;Horn, Susanne
在木星表面观察到的大规模方位角喷流的阻尼机制尚不清楚，但电磁力被怀疑在行星的电导率随深度径向增加时发挥作用。为了隔离射流阻尼过程，我们进行了一套直接数值模拟的准二维，水平周期性瑞利-贝纳德对流与无应力边界条件下的存在下，外部，垂直磁场。当磁场相对较弱时，在瑞利数（浮力与扩散之比）超过时，喷流发展，并被间歇性的对流爆发打断。五个主要的流动状态被发现通过改变和的amerasekhar数（，洛伦兹粘度比）：（i）稳定的对流卷，（ii）稳定的磁柱，（iii）不稳定的湍流磁羽流，（iv）水平漂移磁羽流，和（v）射流与间歇性湍流对流爆发。我们解析的参数空间使用来自相互作用参数（洛伦兹惯性比）的转换。由喷气机为主的政权的过渡有最直接的应用程序的木星喷流的磁阻尼，其中发生在基于喷气的相互作用参数值的喷气机和磁约束系统之间的分离。我们近似的木星相互作用参数的值作为深度的函数，并发现喷流可能制动atkm以下的表面，这是深于最近的估计从美国宇航局的朱诺使命。这表明，除了电磁力之外，可能还需要其他机制来完全截断射流。
The mechanism responsible for the damping of the large-scale, azimuthally directed jets observed at Jupiter's surface is not well known, but electromagnetic forces are suspected to play a role as the planet's electrical conductivity increases radially with depth. To isolate the jet damping process, we carry out a suite of direct numerical simulations of quasi-two-dimensional, horizontally periodic Rayleigh-Bénard convection with stress-free boundary conditions in the presence of an external, vertical magnetic field. Jets, punctuated by intermittent convective bursts, develop at Rayleigh numbers (, ratio of buoyancy to diffusion) beyondwhen the magnetic field is relatively weak. Five primary flow regimes are found by varyingand the Chandrasekhar number (, ratio of Lorentz to viscosity): (i) steady convection rolls, (ii) steady magneto-columns, (iii) unsteady to turbulent magneto-plumes, (iv) horizontally drifting magneto-plumes, and (v) jets with intermittent turbulent convective bursts. We parse the parameter space using transitions derived from the interaction parameter (, ratio of Lorentz to inertia). The transition to the regime dominated by jets has the most immediate applications to the magnetic damping of Jovian jet flows, where the separation between jets and a magnetically constrained system occurs at a jet-based interaction parameter value of. We approximate the value of the Jovian interaction parameter as a function of depth, and find that the jets may brake atkm below the surface, which is deeper than recent estimates from NASA's Juno mission. This suggests that mechanisms in addition to electromagnetic forces are likely required to fully truncate the jets.