Turbulence Power Spectra in Regions Surrounding Jupiter's South Polar Cyclones From Juno/JIRAM
Turbulence Power Spectra in Regions Surrounding Jupiter's South Polar Cyclones From Juno/JIRAM
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来自 Juno/JIRAM 的木星南极气旋周围区域的湍流功率谱
DOI：
10.1029/2019je006096
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发表时间：
2020
期刊：
影响因子：
--
通讯作者：
A. Olivieri
中科院分区：
文献类型：
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作者：
M. Moriconi;A. Migliorini;F. Altieri;A. Adriani;Alessandro Mura;Glenn S Orton;J. Lunine;Davide Grassi;Sushil K. Atreya;A. Ingersoll;B. Dinelli;S. Bolton;S. Levin;F. Tosi;R. Noschese;C. Plainaki;A. Cicchetti;G. Sindoni;A. Olivieri
我们对木星南极附近的两个狭窄环形区域进行了功率谱分析，这些区域是根据美国宇航局朱诺号任务上的木星红外极光测绘仪获取的数据得出的。我们的分析特别关注木星红外极光测绘仪 M 波段成像仪（以下简称 IMG-M）获取的数据集，该成像仪在以 4.8 μm 为中心的光谱窗口中探测木星的热发射。我们分析了在六次朱诺近周期间获取的图像上旋风分离器外部和内部的圆形路径的功率谱密度。典型的空间分辨率约为 55 公里像素−1。我们的分析仅限于 2017 年 2 月至 2018 年 5 月对南极的六次采集。极环外部和内部的功率谱密度似乎遵循两种不同的幂律。波数分别遵循-0.9 ± 0.2（内部）和-1.2 ± 0.2（外部）以及-3.2 ± 0.3（内部）和-3.4 ± 0.2（外部）的平均幂律，位于~2 × 10−3 km−1 波数的斜坡过渡下方和上方。这种光谱行为是二维湍流的典型特征。我们将对应于坡度过渡的 500 公里长度尺度解释为罗斯贝变形半径。它与分析区域中可见的涡流特征子集的尺寸兼容，表明可能存在斜压不稳定性。如果是这样，则意味着准地转近似在这种情况下是有效的。
We present a power spectral analysis of two narrow annular regions near Jupiter's South Pole derived from data acquired by the Jovian Infrared Auroral Mapper instrument onboard NASA's Juno mission. In particular, our analysis focuses on the data set acquired by the Jovian Infrared Auroral Mapper M‐band imager (hereafter IMG‐M) that probes Jupiter's thermal emission in a spectral window centered at 4.8 μm. We analyze the power spectral densities of circular paths outside and inside of cyclones on images acquired during six Juno perijoves. The typical spatial resolution is around 55 km pixel−1. We limited our analysis to six acquisitions of the South Pole from February 2017 to May 2018. The power spectral densities both outside and inside the circumpolar ring seem to follow two different power laws. The wave numbers follow average power laws of −0.9 ± 0.2 (inside) and −1.2 ± 0.2 (outside) and of −3.2 ± 0.3 (inside) and −3.4 ± 0.2 (outside), respectively, beneath and above the transition in slope located at ~2 × 10−3 km−1 wave number. This kind of spectral behavior is typical of two‐dimensional turbulence. We interpret the 500 km length scale, corresponding to the transition in slope, as the Rossby deformation radius. It is compatible with the dimensions of a subset of eddy features visible in the regions analyzed, suggesting that a baroclinic instability may exist. If so, it means that the quasi‐geostrophic approximation is valid in this context.
面积公式和光谱密度
DOI：
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发表时间：
2019
期刊：
影响因子：
--
作者：
楳田登美男
通讯作者：
楳田登美男