The Juno spacecraft, which is in a polar orbit around Jupiter, is providing direct measurements of the planet’s magnetic field close to its surface1. A recent analysis of observations of Jupiter’s magnetic field from eight (of the first nine) Juno orbits has provided a spherical-harmonic reference model (JRM09)2 of Jupiter’s magnetic field outside the planet. This model is of particular interest for understanding processes in Jupiter’s magnetosphere, but to study the field within the planet and thus the dynamo mechanism that is responsible for generating Jupiter’s main magnetic field, alternative models are preferred. Here we report maps of the magnetic field at a range of depths within Jupiter. We find that Jupiter’s magnetic field is different from all other known planetary magnetic fields. Within Jupiter, most of the flux emerges from the dynamo region in a narrow band in the northern hemisphere, some of which returns through an intense, isolated flux patch near the equator. Elsewhere, the field is much weaker. The non-dipolar part of the field is confined almost entirely to the northern hemisphere, so there the field is strongly non-dipolar and in the southern hemisphere it is predominantly dipolar. We suggest that Jupiter’s dynamo, unlike Earth’s, does not operate in a thick, homogeneous shell, and we propose that this unexpected field morphology arises from radial variations, possibly including layering, in density or electrical conductivity, or both.Maps of Jupiter’s internal magnetic field at a range of depths reveal an unusual morphology, suggesting that Jupiter’s dynamo, unlike Earth’s, does not operate in a thick, homogeneous shell.

中文翻译：

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从木星磁场的半球二分法推断出的复杂发电机

朱诺号航天器位于环绕木星的极地轨道上，正在直接测量木星表面附近的磁场1。最近对来自八个（前九个）朱诺轨道的木星磁场观测的分析提供了木星行星外磁场的球谐参考模型 (JRM09)2。该模型对于理解木星磁层中的过程特别有用，但要研究行星内的磁场以及负责产生木星主磁场的发电机机制，则首选替代模型。在这里，我们报告了木星内一系列深度的磁场图。我们发现木星的磁场不同于所有其他已知的行星磁场。在木星内部，大部分通量来自北半球狭窄带中的发电机区域，其中一些通量通过赤道附近的强烈孤立通量斑块返回。在其他地方，该领域要弱得多。场的非偶极部分几乎完全局限于北半球，因此该场是强非偶极场，而在南半球则主要是偶极场。我们认为木星的发电机与地球的发电机不同，它不是在厚的、均质的外壳中运行，我们认为这种意想不到的磁场形态源于径向变化，可能包括分层、密度或电导率，或两者兼而有之。 木星内部磁力图一系列深度的磁场揭示了一种不寻常的形态，这表明木星的发电机与地球不同，它不是在厚而均匀的外壳中运行。