Pith. sign in

REVIEW 2 major objections 5 minor 86 references

Core-surface kinematic control of polarity reversals in advanced geodynamo simulations

T0 review · 2 major / 5 minor · reviewed 2026-08-15 · deepseek-v4-flash

Pith's one-line read A kinematic competition between core-surface upwellings and circulation, measured by $\tau_{\rm exp}/\tau_{\rm surf}$, controls dipole strength and polarity reversals independently of the interior force balance.

desk verdict A genuinely new reversal mechanism for geodynamo models, backed by a solid 41-case survey, but the Earth extrapolation rests on a self-cited path theory tested at only two points. read the letter →

arxiv 2505.05221 v1 pith:6MGDQOQO submitted 2025-05-08 physics.geo-ph

classification physics.geo-ph
keywords Earth'scoreGeomagnetismGeodynamoPolarityreversalsExcursionsMagnetohydrodynamicsCore-surfaceupwellingsStabletop
verification ladder T0 review T1 audit T2 compute T3 formal

The pith

A machine-rendered reading of the paper's core claim, the machinery that carries it, and where it could break.

The reading

The paper sets out to replace the standard inertial explanation of geomagnetic polarity reversals with a purely kinematic one: what decides whether the axial dipole is strong and stable or weak and reversing is the relative strength of subsurface upwellings and horizontal circulation at the core surface, expressed by the time-scale ratio $\tau_{\rm exp}/\tau_{\rm surf}$. Using a suite of 41 geodynamo simulations with bottom-driven buoyancy from inner-core freezing, the authors show that weakening subsurface upwellings—by imposing stable stratification at the top of the core—monotonically lowers the time-averaged dipole and raises its relative fluctuations, with reversals appearing once those fluctuations exceed about a third of the mean. Because the mechanism operates through the induction equation alone and does not depend on the interior force balance, the authors argue it carries over to Earth's core conditions, where the inertial transition invoked by earlier models is thought to be unattainable. The stakes are concrete: if the claim is right, a single model with a weakly stratified top can reproduce geomagnetic variation from decades to millions of years, and the long-assumed link between mantle heat flow and reversal frequency is reversed.

What carries the argument

The central object is the time-scale ratio $\tau_{\rm exp}/\tau_{\rm surf} = U_{\rm surf}/(W\delta)$, where $U_{\rm surf}$ is the root-mean-squared core-surface circulation, $W$ is the strength of subsurface upwellings (the radial derivative of radial velocity at the surface), and $\delta$ is the thickness of the magnetic boundary layer beneath the core surface. $\tau_{\rm exp}$ is the time scale for magnetic flux expulsion by upwellings and $\tau_{\rm surf}$ is the time scale for the gyre-like surface circulation to advect flux patches poleward. Upwellings create new magnetic flux of normal polarity near the equator; if the surface circulation removes that flux before it can build up, the dipole is weakened. The paper uses a budget equation for the axial dipole at the core surface to separate inductive creation (by divergent and non-divergent flows) from diffusive destruction, and shows that stabilizing the top of the core reduces $W$, raises $\tau_{\rm exp}/\tau_{\rm surf}$, and converts a stable dipolar dynamo into a reversing one.

What would settle it

A decisive test would be to measure, in a single bottom-driven dynamo at $\mathrm{Rm} > 1500$, whether changing only the surface circulation strength—without any change in stratification or upwelling—reproduces the same dipole attenuation and reversal threshold as changing the upwelling strength; if dipole amplitude is not a function of $\tau_{\rm exp}/\tau_{\rm surf}$ alone, the kinematic control is not established. A separate test of the geophysical extrapolation would be the detection of a strongly stratified top-core layer ($N \approx 10^{-3}\,\mathrm{s}^{-1}$ over roughly 300 km), which the paper itself shows would permanently suppress the dipole and thus falsify its weak-stratification scenario.

Watch

Extended reading notes

Core claim

Using bottom-driven convection with buoyancy supplied by inner-core freezing, the paper demonstrates that the long-term amplitude of the axial dipole is set by a competition between two surface processes: magnetic flux expulsion by subsurface upwellings, on a time scale $\tau_{\rm exp} = \delta/W$, and poleward advection by the large-scale surface circulation, on a time scale $\tau_{\rm surf} = D/U_{\rm surf}$. As the ratio $\tau_{\rm exp}/\tau_{\rm surf}$ increases (upwellings weakened relative to circulation), the time-averaged dipole decreases monotonically while its fluctuations stay nearly constant; reversals occur when the fluctuation level reaches about one-third of the mean. The same effect is obtained whether the top of the core is homogeneously stabilized, regionally stabilized by tomographic mantle heat-flow heterogeneity, or simply evolved along a parameter-space path toward Earth's core conditions, and it operates while the quasi-geostrophic magneto-Archimedes-Coriolis force balance is preserved with magnetic-to-kinetic energy ratios above ten. The authors conclude that reversals caused by this stable-top-core mechanism are kinematic in origin and therefore expected to apply at Earth's core conditions.

Load-bearing premise

The paper's claim that the mechanism operates in Earth's core rests on the assumption that the leading-order force balance of the models (pressure, Coriolis, buoyancy and magnetic forces, with inertia subdominant) remains unchanged when results are scaled to Earth's core conditions; if that invariance fails, the reversal mechanism may be a numerical artifact.

Editorial extensions

If this is right

  • Reversal frequency can be set by the degree of top-core stratification instead of by convective forcing, so a model can reproduce the observed reversal rate without sacrificing the rest of the geomagnetic spectrum.
  • With weak stratification corresponding to a nearly adiabatic core-surface heat flow, one model matches observed geomagnetic variation from decadal through million-year time scales while satisfying morphological and paleomagnetic criteria.
  • In this mechanism, increasing stratification (decreasing core heat flow) makes reversals more frequent, directly opposite to the forcing-driven paradigm; this reverses the inferred sign of the mantle-to-core heat-flow control on reversal rate.
  • Reversals can proceed while the interior force balance remains quasi-geostrophic magneto-Archimedes-Coriolis, with magnetic-to-kinetic energy ratios above ten, so the mechanism is not tied to inertial effects and is expected to hold at Earth's core conditions.
  • Strong stable stratification is incompatible with an Earth-like dipole; the admissible strength is about $N < 10^{-5}\,\mathrm{s}^{-1}$ for a 10-km layer, implying $Q_{\rm ad} - Q_{\rm CMB} < 10^{-2}\,\mathrm{TW}$, so sustained superchrons or reversal hyperactivity could reflect small fluctuations of core heat flow around the adiabatic value.

Reading between the lines

Editorial extensions of the paper, not claims the author makes directly.

  • If reversal frequency is set by $\tau_{\rm exp}/\tau_{\rm surf}$ rather than by forcing, the polarity record becomes a sensitive recorder of the difference between actual and adiabatic core heat flow; tiny mantle-driven fluctuations around $Q_{\rm ad}$ could produce pronounced alternations between superchrons and reversal hyperactivity.
  • Because the control is kinematic, the dipole's stochastic behaviour may be captured by models that treat the induction equation as the dynamical system and convection as random forcing; combining this paper's mean-dipole control with a complementary strategy that directly controls fluctuation levels could jointly satisfy all paleomagnetic criteria without fine-tuning.
  • A testable extension is to check whether reversal frequency collapses onto a universal function of $\tau_{\rm exp}/\tau_{\rm surf}$ across different ways of stabilizing the top core (uniform stratification, tomographic heat-flow heterogeneity, or other mechanisms); if it does, the surface flow geometry rather than the specific stabilization mechanism is the controlling variable.
  • The mechanism implies that regional stable zones beneath hot lower-mantle provinces may locally suppress upwellings and act as preferred sites for reversal initiation; if so, the statistics of reversals and excursions could serve as a probe of lowermost-mantle thermal structure.
Share X Bluesky LinkedIn Reddit HN

Signed reviews

No signed human review yet.

Editorial analysis

A structured set of objections, weighed in public.

Desk editor's note, referee report, and a circularity audit.

Referee Report

2 major / 5 minor

Summary. The paper proposes a new mechanism for geomagnetic polarity reversals in numerical dynamo simulations. Using a suite of 41 models with bottom-driven buoyancy, the authors show that the time-averaged axial dipole amplitude decreases monotonically as the ratio tau_exp/tau_surf increases, where tau_exp is the magnetic flux expulsion time by subsurface upwellings and tau_surf is the surface circulation time. Increasing the stability of the outermost core weakens upwellings, raises this ratio, and eventually produces reversals when dipole fluctuations exceed roughly one third of the mean. The mechanism is argued to be kinematic, operating independently of the interior force balance, and is therefore claimed to apply at Earth's core conditions. A single model with weak stable stratification is shown to reproduce many observed geomagnetic and paleomagnetic properties, from secular variation timescales to reversal and excursion rates. The paper contrasts this 'stable top core' mechanism with the classical forcing-driven, inertia-based reversal paradigm and discusses implications for core heat flow, superchrons, and inner-core age.

Significance. If the central claim holds, this is a substantial contribution: it offers a reversal mechanism that sidesteps the long-standing problem that inertia-based reversal criteria are unrealistically strong at Earth's core conditions, and it reverses the sign of the predicted relationship between core heat flow and reversal frequency. The study's strengths include a systematic 41-case survey, paired comparisons along parameter-space paths (Stable top 0% vs 29%), reproduction of the previously published volumetric-forcing behavior as a control, explicit force-balance analysis during reversals, and quantitative comparisons against geomagnetic and paleomagnetic compliance criteria. The paper is also commendably candid about its remaining limitations, including the need for fine-tuning of stratification and the incomplete adherence to all paleomagnetic criteria. The empirical collapse in Fig. 4 is a genuine and useful result regardless of whether the geophysical extrapolation is fully accepted.

major comments (2)
  1. [§3.4 and §2.3, Figs. 7-8] The geophysical applicability claim rests on the invariance of the surface time-scale ratio tau_exp/tau_surf along parameter-space paths toward Earth's core conditions. The only direct evidence is the Stable top 0%/29% pair, which spans about one decade in magnetic Ekman number (E_eta from 7.5e-6 to 7.5e-7), whereas Earth's E_eta is roughly 2e-9, two to three more decades away. Moreover, tau_exp/tau_surf = U_surf/(W*delta) is a diagnostic output, not a control parameter: it is only indirectly influenced by the imposed stratification strength N and layer thickness H. The text states that the ratio can be 'assigned' a constant value along a path, but no scaling law or control procedure is given for how N, H, or the surface flow statistics should evolve along the remaining path. The abstract's assertion that the mechanism 'is therefore expected to apply at the physical conditions of Earth's core' is consequently not fully supported by the presented evidence. I recommend either adding path positions beyond 29% (or a demonstrated scaling of U_surf, W, and delta with E_eta under the QG-MAC balance), or softening the extrapolation claim to an explicitly conditional statement.
  2. [§3.2 and §4.1, Fig. 4] The paper describes the mechanism as 'purely kinematic' and 'irrespective of the interior force balance,' but its own results show that the control by tau_exp/tau_surf only operates for bottom-driven convection with magnetic Reynolds number above roughly 1000: volumetric-forcing cases (Vol) fall off the Fig. 4 trend, and low-Rm bottom-driven cases (triangles in Fig. 4b) do not reverse. These exceptions do not involve a change in the interior force balance, so they do not contradict the QG-MAC invariance per se, but they show that the kinematic ratio is not by itself sufficient: the surface magnetic diffusion balance, which depends on the interior buoyancy distribution and on Rm, is also part of the causal chain. The text should either state the precise regime of validity (e.g., 'in bottom-driven, high-Rm dynamos with a surface boundary-layer structure of the form assumed in Eq. 7'), or demonstrate that the Rm range and bottom-driven condition are themselves guaranteed at Earth's core conditions under the high-conductivity hypothesis.
minor comments (5)
  1. [Abstract] The abstract states that 'a single model reproduces the observed geomagnetic variations ranging from decades to millions of years.' This overstates the spectral agreement shown in Fig. 1d, where the model overpredicts sedimentary long-period power by a factor of 3-4, and the model passes only 3 of 5 paleomagnetic criteria (QPM=3). Please qualify the claim, e.g., 'reproduces the overall spectral shape and several morphological criteria,' or explicitly mention the long-period overprediction in the abstract.
  2. [§4.2, Eq. (10)] The statement that 'virtually any sub-adiabatic heat flow will cause the destruction of the dipole' is a strong conclusion derived from the condition N < 1e-5 s^-1 for H=10 km and Eq. (10). This result should be accompanied by a sensitivity estimate for the uncertainties in thermal conductivity k and expansion coefficient alpha, since the allowed heat flow deficit scales linearly with k and inversely with alpha and would change if the parameter values from appendix A are revised.
  3. [§2.3, Eq. (8)] The definition of the path position beta is ambiguous: the text says beta is an integer position along a 7-decade path, but the formula E_eta(EOP) = sqrt(10^(beta-7)) E_eta(model) makes it unclear whether beta=0 or beta=7 corresponds to the model and to Earth. Please clarify the direction of the path and give a worked example (e.g., for the Stable top 0% model).
  4. [Table 1 and supplementary tables] Since tau_exp/tau_surf is the central control parameter, please report its values explicitly for the selected models in Table 1 (and ideally in the supplementary tables for all 41 cases). Currently the reader must infer the ratio from U_surf, W, and delta, which are not all listed for the selected cases.
  5. [§3.2, Fig. 4b] The statement 'Reversals are found to occur when fluctuations exceed a third of the average' is based on visual inspection of the scatter in Fig. 4b without uncertainty quantification. Given the overlap between reversing and non-reversing symbols at intermediate fluctuation levels, a simple statistical characterization (e.g., a logistic fit with confidence bands, or at least a statement of the number of exceptions to the threshold) would strengthen the claim.

Circularity Check

0 steps flagged · score 1.0 of 10

No significant circularity: the model-level control relation is in-sample but not definitionally forced, and the Earth extrapolation rests on a stated path-theory assumption rather than on a circular reduction.

full rationale

The paper's central relation is between the diagnosed time-scale ratio tau_exp/tau_surf = U_surf/(W delta) and the axial dipole amplitude across 41 model cases. This ratio is not defined in terms of the dipole amplitude; it is computed from surface-flow and magnetic-dissipation diagnostics, so the correlation is not self-definitional. The causal claim is supported by paired models that differ only in the presence and strength of the stable top layer while holding convective forcing and other inputs fixed, so it is not simply a fitted-parameter relabeled as a prediction. The main extrapolation to Earth's core invokes the authors' path theory (Aubert et al. 2017; Aubert 2023) to preserve the QG-MAC force balance, and the paper additionally assigns a constant value to tau_exp/tau_surf over the path. This is a stated, testable assumption rather than a circular reduction: the path theory does not incorporate the reversal mechanism as an input, and the two-point (0% and 29%) comparison provides a partial check. The paper also honestly acknowledges that fine-tuning of stratification is required to match the reversal rate, which is a limitation on predictive power but not a circularity. No equation is equivalent to its own input, and no fitted parameter is disguised as a prediction. Therefore no significant circularity is found.

Assumptions & free parameters 4 free parameters · 5 assumptions · 0 invented entities

The central claim rests on the diagnostic ratio tau_exp/tau_surf, which is computed from model outputs rather than derived from external data. The model control parameters (stratification strength N, layer thickness H, convective power P, and lateral heat flux heterogeneity for Het cases) are set by hand or tuned to match observed reversal rate and secular variation time scale. No new physical entities are introduced. The applicability to Earth's core relies on the self-cited path theory, which is the main domain assumption.

free parameters (4)
  • Stratification strength N (or dimensionless N/N0) = N/N0 = 282.1 for the Stable top model; Earth-like reversal rate found for N about 1e-5 s^-1 with H = 10 km
    The amplitude of the stable layer's adverse density gradient is tuned to obtain the present-day reversal rate of 2-3/Myr; the paper acknowledges fine-tuning in Section 4.1.
  • Stable layer thickness H = 10-290 km across cases; maximum admissible N depends on H
    Varied by hand to explore the mechanism; the combination (N,H) controls tau_exp/tau_surf.
  • Convective power P (or Rayleigh number Ra_F) = P about 3 TW for the baseline model, chosen so tau1_SV about 455 yr
    Adjusted to match the observed secular variation time scale; a control parameter fitted to observations.
  • Tomographic heat flow heterogeneity Delta f/f0 (for Het cases) = Delta q about 200 mW/m^2 peak-to-peak for Earth-like reversal rate
    Imposed lateral mass anomaly flux amplitude at the outer boundary, adjusted to match reversal frequency; less fine-tuning needed than for uniform stable layer.
assumptions (5)
  • domain assumption Boussinesq and magnetohydrodynamic approximations for the outer core flow.
    Used throughout Section 2.1 to model velocity, magnetic field, and density anomaly; standard in geodynamo simulations but not valid for all core processes such as compressibility.
  • domain assumption High core thermal and electrical conductivity (k about 100 W/m/K, sigma about 1e6 S/m) from ab initio computations.
    Needed to obtain the high magnetic Reynolds numbers (950-2100) and the subadiabatic heat flow scenario that underlies the stable top core; cited to Davies et al. (2015). If conductivity is lower, the mechanism may not apply.
  • domain assumption Path-theory invariance of the leading-order QG-MAC force balance along parameter space paths toward Earth's core conditions.
    Section 2.3 uses this to dimensionize model outputs; Section 3.4 uses it to assert the reversal mechanism carries over to Earth's core. It is a self-cited framework (Aubert et al. 2017; Aubert 2023) and is the main support for geophysical applicability.
  • domain assumption The magnetic boundary layer thickness delta from the magnetic dissipation length scale determines the flux expulsion time via tau_exp = D/(W delta).
    Section 2.2 adopts this scaling based on kinematic flux expulsion models (Troyano et al. 2020); the relation between delta and the expulsion time is not derived from first principles here.
  • domain assumption Stress-free mechanical boundary conditions at the outer boundary do not alter the reversal mechanism.
    Section 2.1 states that surface flow and magnetic diffusion under stress-free conditions correspond to those below the viscous boundary layer in no-slip cases, and that the reversal mechanism is unchanged, but this is checked for corresponding cases, not the full survey.

how reviews work

0 comments
Cite this review

Pith. "Pith review of Core-surface kinematic control of polarity reversals in advanced geodynamo simulations." pith.science (2026). https://pith.science/paper/6MGDQOQO

@misc{pith2026250505221,
  author       = {Pith},
  title        = {Pith review of: Core-surface kinematic control of polarity reversals in advanced geodynamo simulations},
  year         = {2026},
  howpublished = {\url{https://pith.science/paper/6MGDQOQO}},
  note         = {Machine review of arXiv:2505.05221}
}
read the original abstract

The geomagnetic field has undergone hundreds of polarity reversals over Earth's history, at a variable pace. In numerical models of Earth's core dynamics, reversals occur with increasing frequency when the convective forcing is increased past a critical level. This transition has previously been related to the influence of inertia in the force balance. Because this force is subdominant in Earth's core, concerns have been raised regarding the geophysical applicability of this paradigm. Reproducing the reversal rate of the past million years also requires forcing conditions that do not guarantee that the rest of the geomagnetic variation spectrum is reproduced. These issues motivate the search for alternative reversal mechanisms. Using a suite of numerical models where buoyancy is provided at the bottom of the core by inner-core freezing, we show that the magnetic dipole amplitude is controlled by the relative strength of subsurface upwellings and horizontal circulation at the core surface. A relative weakening of upwellings brings the system from a stable to a reversing dipole state. This mechanism is purely kinematic because it operates irrespectively of the interior force balance. It is therefore expected to apply at the physical conditions of Earth's core. Subsurface upwellings may be impeded by stable stratification in the outermost core. We show that with weak stratification levels corresponding to a nearly adiabatic core surface heat flow, a single model reproduces the observed geomagnetic variations ranging from decades to millions of years. \rev{In contrast with} the existing paradigm, reversals caused by this stable top core mechanism become more frequent when the level of stratification increases i.e. when the core heat flow decreases. This suggests that the link between mantle dynamics and magnetic reversal frequency needs to be reexamined.

Figures

Figures reproduced from arXiv: 2505.05221 by the authors.

Figure 1
Figure 1. a: Time series of the axial dipole amplitude 𝑔 0 1 obtained in the Stable top and Neutral top models. b: Hammer projections of the radial magnetic field at the core surface (filtered at spherical harmonic degree 13, orange is outwards) before, during and after a polarity reversal from the Stable top model, compared to the present-day structure from the International Reference Geomagnetic Field model (Alken et al., 2… view at source ↗
Figure 2
Figure 2. Time series of (a) the dipole latitude 𝜆𝑑 , (b) the average paleosecular variation index (Panovska and Constable, 2017) over sites evenly distributed at the Earth surface, in the temporal sequence from the Stable top model. Reversals (red dashed vertical lines) and excursions (blue dashed lines) are detected with dipole latitudes less than 45 degrees away from the equator (orange lines in panel a) and spikes in the … view at source ↗
Figure 3
Figure 3. a: Latitudinal profiles of the time-averaged con￾tributions from core surface flow and magnetic diffusion to the variation d𝑔 0 1 ∕d𝑡 of the axial dipole, in the Neutral top model. Presented are the integrands in equation (9), obtained from a 177 kyr-long subset during which the surface flow, the magnetic field and its gradients have been recorded at the native resolution of the model. Contributions constructive to … view at source ↗
Figures from the paper (4 more)
Figure 4
Figure 4. Figure 4: a: Time-averaged absolute axial dipole coefficient ⟨ |𝑔 0 1 | ⟩ as a function of the time scale ratio 𝜏exp∕𝜏surf = 𝑈surf∕𝑊 𝛿 between magnetic flux expulsion by subsurface upwellings and surface circulation. An estimate of ⟨ |𝑔 0 1 | ⟩ for Earth in the past 2 Ma is repo…
Figure 6
Figure 6. Figure 6: a,c,e: Time series of axial dipole moments in model cases 11, Tomographic and Stable top (supplementary Tables 1,2). b,d,f: Skewness of trends in the dipole moment time series (computed as in Buffett, 2023), plotted as a function of the width of the temporal window ove…
Figure 7
Figure 7. Figure 7: Time series of (a) the axial dipole coefficient 𝑔 0 1 , (b) the dipole latitude 𝜆𝑑 , and (c) the interior magnetic to kinetic energy ratio 𝐸mag∕𝐸kin obtained in the Stable top 0% and 29% models, which only differ by their distance to Earth’s core conditions along the s…
Figure 8
Figure 8. Figure 8: Root-mean-squared amplitudes of the forces (computed as in Aubert et al., 2017) acting on the fluid core, normalised with the peak of the pressure force and represented as a function of the spherical harmonic degree 𝓁 in states of (a,c) normal and (b,d) reversing polar…

Discussion (0). Continue with ORCID to comment.

Reference graph

Works this paper leans on

86 extracted references · 45 canonical work pages

  1. [1]

    , author Th \'e bault, E

    author Alken, P. , author Th \'e bault, E. , author Beggan, C.D. , author Amit, H. , author Aubert, J. , author Baerenzung, J. , author Bondar, T.N. , author Brown, W.J. , author Califf, S. , author Chambodut, A. , author Chulliat, A. , author Cox, G.A. , author Finlay, C.C. , author Fournier, A. , author Gillet, N. , author Grayver, A. , author Hammer, M...

  2. [2]

    , year 2018

    author Aubert, J. , year 2018 . title Geomagnetic acceleration and rapid hydromagnetic wave dynamics in advanced numerical simulations of the geodynamo . journal Geophys. J. Int. volume 214 , pages 531--547 . :10.1093/gji/ggy161

  3. [3]

    , year 2019

    author Aubert, J. , year 2019 . title Approaching Earth's core conditions in high-resolution geodynamo simulations . journal Geophys. J. Int. volume 219 , pages S137--S151 . :10.1093/gji/ggz232

  4. [4]

    , year 2023

    author Aubert, J. , year 2023 . title State and evolution of the geodynamo from numerical models reaching the physical conditions of Earth's core . journal Geophys. J. Int. volume 235 , pages 468--487 . :10.1093/gji/ggad229

  5. [5]

    , year 2025

    author Aubert, J. , year 2025 . title Rapid geomagnetic variations and stable stratification at the top of Earth's core . journal Phys. Earth Planet. Int. volume 362 , pages 107335 . :https://doi.org/10.1016/j.pepi.2025.107335

  6. [6]

    , author Amit, H

    author Aubert, J. , author Amit, H. , author Hulot, G. , author Olson, P. , year 2008 . title Thermochemical flows couple the Earth's inner core growth to mantle heterogeneity . journal Nature volume 454 , pages 758--761 . :10.1038/nature07109

  7. [7]

    , author Finlay, C.C

    author Aubert, J. , author Finlay, C.C. , author Fournier, A. , year 2013 . title Bottom-up control of geomagnetic secular variation by the Earth's inner core . journal Nature volume 502 , pages 219--223

  8. [8]

    , author Gastine, T

    author Aubert, J. , author Gastine, T. , author Fournier, A. , year 2017 . title Spherical convective dynamos in the rapidly rotating asymptotic regime . journal J. Fluid. Mech. volume 813 , pages 558--593 . :10.1017/jfm.2016.789

Show all 86 references
  1. [9]

    , author Labrosse, S

    author Aubert, J. , author Labrosse, S. , author Poitou, C. , year 2009 . title Modelling the palaeo-evolution of the geodynamo . journal Geophys. J. Int. volume 179 , pages 1414--1428 . 10.1111/j.1365-246X.2009.04361.x

  2. [10]

    , author Aubert, J

    author Badro, J. , author Aubert, J. , author Hirose, K. , author Nomura, R. , author Blanchard, I. , author Borensztajn, S. , author Siebert, J. , year 2018 . title Magnesium partitioning between earth's mantle and core and its potential to drive an early exsolution geodynamo...

  3. [11]

    , author Gallet, Y

    author Besse, J. , author Gallet, Y. , year 2025 . title Subduction-related volcanic activity as a proxy for global subduction flux over the past billion years, and its correlation with geomagnetic superchrons . journal Geophys. Res. Lett. volume 52 , pages e2024GL111360 . :ht...

  4. [12]

    , author Bono, R.K

    author Biggin, A.J. , author Bono, R.K. , author Meduri, D.G. , author Sprain, C.J. , author Davies, C.J. , author Holme, R. , author Doubrovine, P.V. , year 2020 . title Quantitative estimates of average geomagnetic axial dipole dominance in deep geological time . journal Nat...

  5. [13]

    , author Steinberger, B

    author Biggin, A.J. , author Steinberger, B. , author Aubert, J. , author Suttie, N. , author Holme, R. , author Torsvik, T.H. , author van der Meer, D.G. , author van Hinsbergen, D.J.J. , year 2012 . title Possible links between long-term geomagnetic variations and whole-mant...

  6. [14]

    , author Paterson, G.A

    author Bono, R.K. , author Paterson, G.A. , author van der Boon, A. , author Engbers, Y.A. , author Michael Grappone, J. , author Handford, B. , author Hawkins, L.M.A. , author Lloyd, S.J. , author Sprain, C.J. , author Thallner, D. , author Biggin, A.J. , year 2021 . title Th...

  7. [15]

    , author Fu, R.R

    author Brenner, A.R. , author Fu, R.R. , author Kylander-Clark, A.R.C. , author Hudak, G.J. , author Foley, B.J. , year 2022 . title Plate motion and a dipolar geomagnetic field at 3.25 Ga . journal PNAS volume 119 , pages e2210258119 . :10.1073/pnas.2210258119

  8. [16]

    , year 2014

    author Buffett, B.A. , year 2014 . title Geomagnetic fluctuations reveal stable stratification at the top of the Earth's core . journal Nature volume 507 , pages 484--487 . 10.1038/nature13122

  9. [17]

    , year 2023

    author Buffett, B.A. , year 2023 . title Asymmetric dipole trends in geodynamo models and the paleomagnetic field . journal Geochem. Geophys. Geosyst. volume 24 , pages e2023GC011242 . :https://doi.org/10.1029/2023GC011242

  10. [18]

    , year 2024

    author Buffett, B.A. , year 2024 . title Excursions, reversals, and secular variation: Different expressions of a common mechanism? journal Geochem. Geophys. Geosyst. volume 25 , pages e2024GC011604 . :https://doi.org/10.1029/2024GC011604

  11. [19]

    , author Huppert, H.E

    author Buffett, B.A. , author Huppert, H.E. , author Lister, J.R. , author Woods, A.W. , year 1996 . title On the thermal evolution of the Earth's core . journal J. Geophys. Res. volume 101 , pages 7989--8006

  12. [20]

    , author Amit, H

    author Choblet, G. , author Amit, H. , author Husson, L. , year 2016 . title Constraining mantle convection models with palaeomagnetic reversals record and numerical dynamos . journal Geophysical Journal International volume 207 , pages 1165--1184 . :10.1093/gji/ggw328

  13. [21]

    , year 2018

    author Christensen, U. , year 2018 . title Geodynamo models with a stable layer and heterogeneous heat flow at the top of the core . journal Geophys. J. Int. volume 215 , pages 1338--1351 . :10.1093/gji/ggy352

  14. [22]

    , year 2011

    author Christensen, U.R. , year 2011 . title Geodynamo models: Tools for understanding properties of E arth's magnetic field . journal Phys. Earth Planet. Int. volume 187 , pages 157--169

  15. [23]

    , author Aubert, J

    author Christensen, U.R. , author Aubert, J. , year 2006 . title Scaling properties of convection-driven dynamos in rotating spherical shells and application to planetary magnetic fields . journal Geophys. J. Int. volume 166 , pages 97--114 . :10.1111/j.1365-246X.2006.03009.x

  16. [24]

    , author Aubert, J

    author Christensen, U.R. , author Aubert, J. , author Hulot, G. , year 2010 . title Conditions for Earth-like geodynamo models . journal Earth. Plan. Sci. Let. volume 296 , pages 487--496 . :10.1016/j.epsl.2010.06.009

  17. [25]

    , author Constable, S

    author Constable, C. , author Constable, S. , year 2023 . title A grand spectrum of the geomagnetic field . journal Phys. Earth Planet. Int. volume 344 , pages 107090 . :https://doi.org/10.1016/j.pepi.2023.107090

  18. [26]

    , author Gassmoeller, R

    author Dannberg, J. , author Gassmoeller, R. , author Thallner, D. , author LaCombe, F. , author Sprain, C. , year 2024 . title Changes in core-mantle boundary heat flux patterns throughout the supercontinent cycle . journal Geophys. J. Int. volume 237 , pages 1251--1274

  19. [27]

    , author Pozzo, M

    author Davies, C. , author Pozzo, M. , author Gubbins, D. , author Alf \`e , D. , year 2015 . title Constraints from material properties on the dynamics and evolution of Earth's core . journal Nature Geosci. volume 8 , pages 678--685 . :10.1038/ngeo2492

  20. [28]

    , author Robert, B

    author Domeier, M. , author Robert, B. , author Meert, J.G. , author Kulakov, E.V. , author McCausland, P.J. , author Trindade, R.I. , author Torsvik, T.H. , year 2023 . title The enduring Ediacaran paleomagnetic enigma . journal Earth Sci Rev. volume 242 , pages 104444 . :htt...

  21. [29]

    , author Olson, P

    author Driscoll, P. , author Olson, P. , year 2009 . title Effects of buoyancy and rotation on the polarity reversal frequency of gravitationally driven numerical dynamos . journal Geophys. J. Int. volume 178 , pages 1337--1350 . :10.1111/j.1365-246X.2009.04234.x

  22. [30]

    , author Aubert, J

    author Finlay, C.C. , author Aubert, J. , author Gillet, N. , year 2016 . title Gyre-driven decay of the Earth's magnetic dipole . journal Nature comm. volume 7:10422 . 10.1038/ncomms10422

  23. [31]

    , author Gillet, N

    author Finlay, C.C. , author Gillet, N. , author Aubert, J. , author Livermore, P.W. , author Jault, D. , year 2023 . title Gyres, jets and waves in the Earth's core . journal Nature Reviews Earth & Environ. volume 4 , pages 377--392 . :10.1038/s43017-023-00425-w

  24. [32]

    , author Schaeffer, N

    author Frasson, T. , author Schaeffer, N. , author Nataf, H.C. , author Labrosse, S. , year 2025 . title Geomagnetic dipole stability and zonal flows controlled by mantle heat flux heterogeneities . journal Geophys. J. Int. volume 240 , pages 1481--1504 . :10.1093/gji/ggae457

  25. [33]

    , author Avery, M.S

    author Frost, D.A. , author Avery, M.S. , author Buffett, B.A. , author Chidester, B.A. , author Deng, J. , author Dorfman, S.M. , author Li, Z. , author Liu, L. , author Lv, M. , author Martin, J.F. , year 2022 . title Multidisciplinary constraints on the thermal-chemical bou...

  26. [34]

    , author Pavlov, V

    author Gallet, Y. , author Pavlov, V. , author Korovnikov, I. , year 2019 . title Extreme geomagnetic reversal frequency during the middle cambrian as revealed by the magnetostratigraphy of the khorbusuonka section (northeastern siberia) . journal Earth Planet. Sci. Lett. volu...

  27. [35]

    , author Pavlov, V.E

    author Gallet, Y. , author Pavlov, V.E. , year 2016 . title Three distinct reversing modes in the geodynamo . journal Izvestiya volume 52 , pages 291--296 . :10.1134/S106935131602004X

  28. [36]

    , author Aubert, J

    author Gastine, T. , author Aubert, J. , author Fournier, A. , year 2020 . title Dynamo-based limit to the extent of a stable layer atop Earth's core . journal Geophys. J. Int. volume 222 , pages 1433--1448 . :10.1093/gji/ggaa250

  29. [37]

    , author Roberts, P

    author Glatzmaier, G. , author Roberts, P. , year 1995 . title A 3-dimensional self-consistent computer-simulation of a geomagnetic-field reversal . journal Nature volume 377 , pages 203--209 . 10.1038/377203a0

  30. [38]

    , year 2008

    author Gubbins, D. , year 2008 . title Implication of kinematic dynamo studies for the geodynamo . journal Geophys. J. Int. volume 173 , pages 79--91 . :10.1111/j.1365-246X.2007.03707.x

  31. [39]

    , author Kaneshima, S

    author Helffrich, G. , author Kaneshima, S. , year 2010 . title Outer-core compositional stratification from observed core wave speed profiles . journal Nature volume 468 , pages 807--810 . 10.1038/nature09636

  32. [40]

    , author Olsen, N

    author Holme, R. , author Olsen, N. , author Bairstow, F.L. , year 2011 . title Mapping geomagnetic secular variation at the core-mantle boundary . journal Geophys. J. Int. volume 186 , pages 521--528 . 10.1111/j.1365-246X.2011.05066.x

  33. [41]

    , author Domeier, M

    author Hounslow, M.W. , author Domeier, M. , author Biggin, A.J. , year 2018 . title Subduction flux modulates the geomagnetic polarity reversal rate . journal Tectonophysics volume 742-743 , pages 34--49 . :https://doi.org/10.1016/j.tecto.2018.05.018

  34. [42]

    , author Amit, H

    author Huguet, L. , author Amit, H. , author Alboussi \`e re, T. , year 2018 . title Geomagnetic dipole changes and upwelling/downwelling at the top of the Earth's Core . journal Frontiers Earth Sci. volume 6 . :10.3389/feart.2018.00170

  35. [43]

    , author Tsang, Y.K

    author Jones, C.A. , author Tsang, Y.K. , year 2025 . title Low inertia reversing geodynamos . journal Phys. Earth. Planet. Int. volume 360 , pages 107303 . :https://doi.org/10.1016/j.pepi.2024.107303

  36. [44]

    , author Christensen, U

    author Kutzner, C. , author Christensen, U. , year 2002 . title From stable dipolar to reversing numerical dynamos . journal Phys. Earth Planet. Int. volume 131 , pages 29--45

  37. [45]

    , year 2015

    author Labrosse, S. , year 2015 . title Thermal evolution of the core with a high thermal conductivity . journal Phys. Earth Planet. Int. volume 247 , pages 36--55 . :https://doi.org/10.1016/j.pepi.2015.02.002

  38. [46]

    , author Channell, J

    author Laj, C. , author Channell, J. , year 2015 . title 5.10 - geomagnetic excursions , in: editor Schubert, G. (Ed.), booktitle Treatise on Geophysics (Second Edition) . edition 2nd. ed.. publisher Elsevier , address Oxford , pp. pages 343--383 . :https://doi.org/10.1016/B97...

  39. [47]

    , author Olson, P

    author Larson, R.L. , author Olson, P. , year 1991 . title Mantle plumes control magnetic reversal frequency . journal Earth Plan. Sci. Lett. volume 107 , pages 437--447 . :https://doi.org/10.1016/0012-821X(91)90091-U

  40. [48]

    , author Fournier, A

    author Lhuillier, F. , author Fournier, A. , author Hulot, G. , author Aubert, J. , year 2011 . title The geomagnetic secular-variation timescale in observations and numerical dynamo models . journal Geophys. Res. Lett. volume 38 , pages L09306 . :10.1029/2011GL047356

  41. [49]

    , year 2003

    author Lister, J.R. , year 2003 . title Expressions for the dissipation driven by convection in the Earth's core . journal Phys. Earth Planet. Int. volume 140 , pages 145--158 . :10.1016/j.pepi.2003.07.007

  42. [50]

    , author Sreenivasan, B

    author Majumder, D. , author Sreenivasan, B. , author Maurya, G. , year 2024 . title Self-similarity of the dipole--multipole transition in rapidly rotating dynamos . journal J. Fluid. Mech. volume 980 , pages A30 . :10.1017/jfm.2024.1

  43. [51]

    , author Laske, G

    author Masters, G. , author Laske, G. , author Bolton, H. , author Dziewonski, A. , year 2000 . title The relative behavior of shear velocity, bulk sound speed, and compressional velocity in the mantle: Implications for chemical and thermal structure , in: editor Karato, S. , ...

  44. [52]

    , author Merrill, R.T

    author McFadden, P.L. , author Merrill, R.T. , author McElhinny, M.W. , year 1988 . title Dipole/quadrupole family modeling of paleosecular variation . journal J. Geophys. Res. volume 93 , pages 11583--11588 . :https://doi.org/10.1029/JB093iB10p11583

  45. [53]

    , author Biggin, A.J

    author Meduri, D.G. , author Biggin, A.J. , author Davies, C.J. , author Bono, R.K. , author Sprain, C.J. , author Wicht, J. , year 2021 . title Numerical dynamo simulations reproduce paleomagnetic field behavior . journal Geophys. Res. Lett. volume 48 , pages e2020GL090544 . ...

  46. [54]

    , author Davies, C

    author Mound, J. , author Davies, C. , author Rost, S. , author Aurnou, J. , year 2019 . title Regional stratification at the top of Earth's core due to core--mantle boundary heat flux variations . journal Nature Geosci. volume 12 , pages 575--580 . :10.1038/s41561-019-0381-z

  47. [55]

    , author Davies, C.J

    author Mound, J.E. , author Davies, C.J. , year 2023 . title Longitudinal structure of Earth's magnetic field controlled by lower mantle heat flow . journal Nature Geosci. volume 16 , pages 380--385 . :10.1038/s41561-023-01148-9

  48. [56]

    , author Davies, C.J

    author Nakagawa, T. , author Davies, C.J. , year 2022 . title Combined dynamical and morphological characterisation of geodynamo simulations . journal Earth Plan. Sci. Lett. volume 594 , pages 117752 . :https://doi.org/10.1016/j.epsl.2022.117752

  49. [57]

    , author Suttie, N

    author Nilsson, A. , author Suttie, N. , author Stoner, J.S. , author Muscheler, R. , year 2022 . title Recurrent ancient geomagnetic field anomalies shed light on future evolution of the South Atlantic Anomaly . journal PNAS volume 119 , pages e2200749119 . :10.1073/pnas.2200749119

  50. [58]

    , year 2015

    author Nimmo, F. , year 2015 . title 9.08 - thermal and compositional evolution of the core , in: editor Schubert, G. (Ed.), booktitle Treatise on Geophysics (Second Edition) . edition 2nd. ed.. publisher Elsevier , address Oxford , pp. pages 201--219 . :https://doi.org/10.101...

  51. [59]

    , year 2020

    author Ogg, J. , year 2020 . title Chapter 5 - geomagnetic polarity time scale , in: editor Gradstein, F.M. , editor Ogg, J.G. , editor Schmitz, M.D. , editor Ogg, G.M. (Eds.), booktitle Geologic Time Scale 2020 . publisher Elsevier , pp. pages 159--192 . :https://doi.org/10.1...

  52. [60]

    , author Amit, H

    author Olson, P. , author Amit, H. , year 2006 . title Changes in Earth's dipole . journal Naturwissenschaften volume 93 , pages 519--542 . :10.1007/s00114-006-0138-6

  53. [61]

    , author Amit, H

    author Olson, P. , author Amit, H. , year 2014 . title Magnetic reversal frequency scaling in dynamos with thermochemical convection . journal Phys. Earth. Planet. Int. volume 229 , pages 122--133

  54. [62]

    , author Christensen, U

    author Olson, P. , author Christensen, U. , author Driscoll, P. , year 2012 . title From superchrons to secular variation: A broadband dynamo frequency spectrum for the geomagnetic dipole . journal Earth. Plan. Sci. Let. volume 319-320 , pages 75--82 . :10.1016/j.epsl.2011.12.008

  55. [63]

    , author Deguen, R

    author Olson, P. , author Deguen, R. , author Hinnov, L.A. , author Zhong, S. , year 2013 . title Controls on geomagnetic reversals and core evolution by mantle convection in the Phanerozoic . journal Phys. Earth. Planet. Int. volume 214 , pages 87--103 . :https://doi.org/10.1...

  56. [64]

    , author Landeau, M

    author Olson, P. , author Landeau, M. , author Reynolds, E. , year 2017 . title Dynamo tests for stratification below the core-mantle boundary . journal Phys. Earth. Planet. Int. volume 271 , pages 1--18 . :https://doi.org/10.1016/j.pepi.2017.07.003

  57. [65]

    , author Constable, C.G

    author Panovska, S. , author Constable, C.G. , year 2017 . title An activity index for geomagnetic paleosecular variation, excursions, and reversals . journal Geochem. Geophys. Geosyst. volume 18 , pages 1366--1375 . :https://doi.org/10.1002/2016GC006668

  58. [66]

    , author Constable, C.G

    author Panovska, S. , author Constable, C.G. , author Korte, M. , year 2018 . title Extending global continuous geomagnetic field reconstructions on timescales beyond human civilization . journal Geochem. Geophys. Geosyst. volume 19 , pages 4757--4772 . :https://doi.org/10.102...

  59. [67]

    , author Fauve, S

    author Petrelis, F. , author Fauve, S. , author Dormy, E. , author Valet, J.P. , year 2009 . title Simple Mechanism for Reversals of Earth's Magnetic Field . journal Phys. Rev. Lett. volume 102 . 10.1103/PhysRevLett.102.144503

  60. [68]

    , author Aubert, J

    author Pichon, G. , author Aubert, J. , author Fournier, A. , year 2016 . title Coupled dynamics of Earth's geomagnetic westward drift and inner core super-rotation . journal Earth Planet. Sci. Lett. volume 437 , pages 114--126

  61. [69]

    , year 2013

    author Schaeffer, N. , year 2013 . title Efficient spherical harmonic transforms aimed at pseudospectral numerical simulations . journal Geophys. Geochem. Geosystems. volume 14 , pages 751--758 . 10.1002/ggge.20071

  62. [70]

    , author Jault, D

    author Schaeffer, N. , author Jault, D. , author Nataf, H.C. , author Fournier, A. , year 2017 . title Turbulent geodynamo simulations: a leap towards E arth's core . journal Geophys. J. Int. volume 211 , pages 1--29 . :10.1093/gji/ggx265

  63. [71]

    , author Gastine, T

    author Schwaiger, T. , author Gastine, T. , author Aubert, J. , year 2019 . title Force balance in numerical geodynamo simulations: a systematic study . journal Geophys. J. Int. volume 219 , pages S101--S114 . :10.1093/gji/ggz192

  64. [72]

    , author Gastine, T

    author Schwaiger, T. , author Gastine, T. , author Aubert, J. , year 2021 . title Relating force balances and flow length scales in geodynamo simulations . journal Geophys. J. Int. volume 224 , pages 1890--1904 . :10.1093/gji/ggaa545

  65. [73]

    , author Biggin, A.J

    author Sprain, C.J. , author Biggin, A.J. , author Davies, C.J. , author Bono, R.K. , author Meduri, D.G. , year 2019 . title An assessment of long duration geodynamo simulations using new paleomagnetic modeling criteria (QPM) . journal Earth Plan. Sci. Lett. volume 526 , page...

  66. [74]

    , author Sahoo, S

    author Sreenivasan, B. , author Sahoo, S. , author Dhama, G. , year 2014 . title The role of buoyancy in polarity reversals of the geodynamo . journal Geophys. J. Int. volume 199 , pages 1698--1708 . :10.1093/gji/ggu340

  67. [75]

    , author Nilsson, A

    author Suttie, N. , author Nilsson, A. , author Gillet, N. , author Dumberry, M. , year 2025 . title Large-scale palaeoflow at the top of earth's core . journal Earth. Plan. Sci. Lett. volume 652 , pages 119185 . :https://doi.org/10.1016/j.epsl.2024.119185

  68. [76]

    , author Gastine, T

    author Tassin, T. , author Gastine, T. , author Fournier, A. , year 2021 . title Geomagnetic semblance and dipolar--multipolar transition in top-heavy double-diffusive geodynamo models . journal Geophys. J. Int. volume 226 , pages 1897--1919 . :10.1093/gji/ggab161

  69. [77]

    , author Amit, H

    author Terra-Nova, F. , author Amit, H. , year 2020 . title Magnetic boundary layers in numerical dynamos with heterogeneous outer boundary heat flux . journal Phys. Earth. Planet. Int. volume 309 , pages 106589 . :10.1016/j.pepi.2020.106589

  70. [78]

    , author Amit, H

    author Terra-Nova, F. , author Amit, H. , year 2024 . title Regionally-triggered geomagnetic reversals . journal Sci. Rep. volume 14 , pages 9639 . :10.1038/s41598-024-59849-z

  71. [79]

    , author Fournier, A

    author Troyano, M. , author Fournier, A. , author Gallet, Y. , author Finlay, C.C. , year 2020 . title Imprint of magnetic flux expulsion at the core--mantle boundary on geomagnetic field intensity variations . journal Geophys. J. Int. volume 221 , pages 1984--2009 . :10.1093/...

  72. [80]

    , author Meynadier, L

    author Valet, J.P. , author Meynadier, L. , year 1993 . title Geomagnetic field intensity and reversals during the past four million years . journal Nature volume 366 , pages 234--238 . :10.1038/366234a0

  73. [81]

    , year 2002

    author Wicht, J. , year 2002 . title Inner-core conductivity in numerical dynamo simulations . journal Phys. Earth Planet. Int. volume 132 , pages 281--302

  74. [82]

    , author Tilgner, A

    author Wicht, J. , author Tilgner, A. , year 2010 . title Theory and modeling of planetary dynamos . journal Space. Sci. Rev. volume 152 , pages 501--542 . :10.1007/s11214-010-9638-y

  75. [83]

    , author Gastine, T

    author Yadav, R.K. , author Gastine, T. , author Christensen, U.R. , author Wolk, S.J. , author Poppenhaeger, K. , year 2016 . title Approaching a realistic force balance in geodynamo simulations . journal PNAS volume 113 , pages 12065--12070 . :10.1073/pnas.1608998113

  76. [84]

    , author Constable, C

    author Ziegler, L. , author Constable, C. , year 2011 . title Asymmetry in growth and decay of the geomagnetic dipole . journal Earth Plan. Sci. Lett. volume 312 , pages 300--304 . :https://doi.org/10.1016/j.epsl.2011.10.019

  77. [85]

    , author Constable, C.G

    author Ziegler, L.B. , author Constable, C.G. , author Johnson, C.L. , author Tauxe, L. , year 2011 . title PADM2M: a penalized maximum likelihood model of the 0--2 Ma palaeomagnetic axial dipole moment . journal Geophys. J. Int. volume 184 , pages 1069--1089 . :10.1111/j.1365...

  78. [86]

    write newline

    " write newline "" before.all 'output.state := FUNCTION n.dashify 't := "" t empty not t #1 #1 substring "-" = t #1 #2 substring "--" = not "--" * t #2 global.max substring 't := t #1 #1 substring "-" = "-" * t #2 global.max substring 't := while if t #1 #1 substring * t #2 gl...

Pith tools

Reviewed August 15, 2026 · model on record in the stance chip above.