[S-CG48] 観測・実験・シミュレーションから見えてきた惑星内部

[SCG48-04] Magnetic Fields of Ice Giant Planets and Their Secular Variation

★Invited Papers

*Chi Yan¹、Krista M Soderlund¹ (1.University of Texas Institute for Geophysics (UTIG))

キーワード：Uranus, Neptune, planetary interiors, dynamo theory, magnetic fields, secular variation

The magnetic fields of the two ice giant planets in our solar system, Uranus and Neptune, are unique due to their strongly non-axisymmetric and non-dipolar features, in contrast to other planetary dynamos in the solar system. Multiple hypotheses have been proposed to explain these features, including dynamo shell thickness, vigorous turbulent convection, and density stratification. Additionally, ab initio and high-pressure experiments suggest that water goes through a rather smooth transition from molecular to ionic phase, leading to radially variable electrical conductivity profiles in addition to changes in the background density stratification.

Here, we use 3D numerical dynamo simulations to investigate the effects of different interior structures tailored for Uranus and Neptune in dynamo behaviors, especially relating to the magnetic field morphology and their secular variation. We find that the existence of the radially variable conductivity and background density stratification can help reproduce some key features of ice giant magnetic fields, such as field morphology and magnetic power spectra. Furthermore, we ask the question: What could we learn about Uranus’ and Neptune’s secular variation? And what should we expect from the future scientific returns of the Uranus Orbiter and Probe mission?
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