木星云层高度的变率由内部的扭转振荡触发
Jupiter's cloud-level variability triggered by torsional oscillations in the interior
AI总结：
本文提出木星内部的磁扭转振荡调制热量传输从而引发对流层带状变率，结合JRM33等模型计算波速，发现其半周期与观测到的木星带区变率循环一致，为研究木星内部动力学提供了新窗口。
摘要：
木星的天气层表现出长期且准周期的气象活动循环，能够完全改变其带和区的外观。这些循环的间隔为4到9年，随纬度而异，在5μm辐射中被探测到，该辐射为对流层的云形成区域提供了一个窗口；然而，这些循环的起源一直是个谜。在此我们提出，源于发电机区域的磁扭转振荡/波可以调制热量传输，从而最终导致对流层带状结构的变率。这些轴对称波是受快速旋转影响的磁流体动力学波，已在地球核心中被探测到，并且最近通过Juno对磁场长期变化的观测，被建议存在于木星上。使用磁场模型JRM33以及密度分布模型，我们计算了这些波的预期速度。对于由纬向急流变化激发的波，其波长可以通过交替急流的宽度来估算，在14-23°N范围内产生半周期为3.2-4.7年的波，这与在可见光和红外观测中识别出的木星北赤道带和北温带变率循环的间隔一致。这些波的性质，包括波速和波长，是通过将数据驱动技术——动态模态分解——应用于5μm发射的时空数据来揭示的。我们的结果表明，探索这些磁流体动力学波可能为木星对流层云中准周期模式的起源，以及木星的内部动力学和发电机，提供一个新的窗口。
英文摘要：
Jupiter's weather layer exhibits long-term and quasi-periodic cycles of meteorological activity that can completely change the appearance of its belts and zones. There are cycles with intervals from 4 to 9 years, dependent on the latitude, which were detected in 5$μ$m radiation, which provides a window into the cloud-forming regions of the troposphere; however, the origin of these cycles has been a mystery. Here we propose that magnetic torsional oscillations/waves arising from the dynamo region could modulate the heat transport and hence be ultimately responsible for the variability of the tropospheric banding. These axisymmetric waves are magnetohydrodynamic waves influenced by the rapid rotation, which have been detected in Earth's core, and have been recently suggested to exist in Jupiter by the observation of magnetic secular variations by Juno. Using the magnetic field model JRM33, together with the density distribution model, we compute the expected speed of these waves. For the waves excited by variations in the zonal jet flows, their wavelength can be estimated from the width of the alternating jets, yielding waves with a half period of 3.2-4.7 years in 14-23$^\circ$N, consistent with the intervals with the cycles of variability of Jupiter's North Equatorial Belt and North Temperate Belt identified in the visible and infrared observations. The nature of these waves, including the wave speed and the wavelength, is revealed by a data-driven technique, dynamic mode decomposition, applied to the spatio-temporal data for 5$μ$m emission. Our results imply that exploration of these magnetohydrodynamic waves may provide a new window to the origins of quasi-periodic patterns in Jupiter's tropospheric clouds and to the internal dynamics and the dynamo of Jupiter.
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