A new model for the (geo)magnetic power spectrum, with application to planetary dynamo radii

Langlais, B.; Amit, Hagay; Larnier, H.; Thébault, Erwan; Mocquet, A.

doi:10.1016/j.epsl.2014.05.013

Cited by 8 publications

(12 citation statements)

References 82 publications

(111 reference statements)

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“…The Lowes radius provides an estimate to the location of the Earth's core-mantle boundary that agrees reasonably with seismic measurement. Langlais et al (2014) found r lowes = 3294.5 km compared to the seismically determined 3481.7 km. Langlais et al (2014) also found that omitting the m = 0 axisymmetric components in (4), so that only the non-zonal components are used,…”

Section: Introductionmentioning

confidence: 63%

“…Langlais et al (2014) found r lowes = 3294.5 km compared to the seismically determined 3481.7 km. Langlais et al (2014) also found that omitting the m = 0 axisymmetric components in (4), so that only the non-zonal components are used,…”

Section: Introductionmentioning

confidence: 63%

“…1(a). However, using the non-zonal components only on the JRM09 data, see equation (8), as suggested by Langlais et al (2014) for the Earth, leads to a better linear fit for l ≥ 6, see Fig. 1(b).…”

Section: Introductionmentioning

confidence: 90%

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Characterising Jupiter's dynamo radius using its magnetic energy spectrum

Tsang

Jones

2020

Earth and Planetary Science Letters

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Jupiter's magnetic field is generated by the convection of liquid metallic hydrogen in its interior. The transition from molecular hydrogen to metallic hydrogen as temperature and pressure increase is believed to be a smooth one. As a result, the electrical conductivity in Jupiter varies continuously from being negligible at the surface to a large value in the deeper region. Thus, unlike the Earth where the upper boundary of the dynamo-the dynamo radius-is definitively located at the core-mantle boundary, it is not clear at what depth dynamo action becomes significant in Jupiter. In this paper, using a numerical model of the Jovian dynamo, we examine the magnetic energy spectrum at different depth and identify a dynamo radius below which (and away from the deep inner core) the shape of the magnetic energy spectrum becomes invariant. We find that this shift in the behaviour of the magnetic energy spectrum signifies a change in the dynamics of the system as electric current becomes important. Traditionally, a characteristic radius derived from the Lowes-Mauersberger spectrum-the Lowes radius-gives a good estimate to the Earth's core-mantle boundary. We argue that in our model, the Lowes radius provides a lower bound to the dynamo radius. We also compare the Lowes-Mauersberger spectrum in our model to that obtained from recent Juno observations. The Lowes radius derived from the Juno data is significantly lower than that obtained from our models. The existence of a stably stratified region in the neighbourhood of the transition zone might provide an explanation of this result.

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Section: Introductionmentioning

confidence: 63%

Section: Introductionmentioning

confidence: 63%

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Characterising Jupiter's dynamo radius using its magnetic energy spectrum

Tsang

Jones

2020

Earth and Planetary Science Letters

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“…We obtained source depths by minimizing the misfit between a source-depth-dependent localized analytical power spectrum and the local power spectra we obtained from our local models. We constructed the localized analytical power spectrum from the global non-zonal power spectrum of Langlais et al (2014) using the localization method of Simons (2005, 2007), with Slepian functions constructed from non-zonal spherical harmonics only. We used a tapering bandwidth of L tap = 3, providing one well-concentrated taper within our region, and used the eigenvalue weighting of Dahlen and Simons (2008) to calculate the local multitaper spectra.…”

Section: Inversion Approachmentioning

confidence: 99%

“…To determine optimal inversion parameters required and to demonstrate that recovery of a source depth from these data is indeed possible, we conducted synthetic tests as follows. We specified a non-zonal magnetic field model following the spectrum by Langlais et al (2014) for a chosen source depth. We used a source radius of km, corresponding to a magnetic source close to Mercury's core-mantle boundary (Genova et al, 2019;Bertone et al, 2021).…”

Section: Synthetic Data Experimentsmentioning

confidence: 99%