The high conductivity of iron and thermal evolution of the Earth’s core

Gomi, Hitoshi; Ohta, Kenji; Hirose, Kei; Labrosse, S.; Caracas, Razvan; Verstraete, Matthieu J.; Hernlund, J. W.

doi:10.1016/j.pepi.2013.07.010

Cited by 270 publications

(414 citation statements)

References 87 publications

Supporting

Mentioning

347

Contrasting

Order By: Relevance

“…Results have only been obtained recently [23][24][25][26][27][28] , and turn out to be 2-3 times higher than conventional estimates 29,30 31 on a perfect iron crystal at ICB conditions suggests that a new effect (electron-electron scattering) would reduce the electrical conductivity back to old values that were estimated for the liquid 29 . The proposed importance of strong correlation effects appears at odds with previous work 32 , so these results await both experimental and theoretical confirmation.…”

mentioning

confidence: 89%

“…Stratified layers are dynamically very different from convecting regions: they suppress radial motion and support a different suite of waves 72 . In the absence of chemical or boundary effects, subadiabatic conditions at the top of the core (Figure 2) Density anomalies associated with core motions are so small that convection is unlikely to entrain or penetrate a stable layer 26,72,75,76 . The effect on a stable layer of thermal anomalies in the lowermost mantle is not so clear.…”

Section: Geophysical Implications Of Revised Core Propertiesmentioning

confidence: 99%

“…The depth increase of k opens up the possibility that the very top of the core is superadiabatic, with a stable layer directly beneath 26,80 . The conditions required to form such a layer are sensitive to the T a (r) and k(r) profiles; the models in this review do not produce such an effect.…”

Section: Geophysical Implications Of Revised Core Propertiesmentioning

confidence: 99%

See 2 more Smart Citations

Constraints from material properties on the dynamics and evolution of Earth’s core

et al. 2015

View full text Add to dashboard Cite

The Earth's magnetic field is powered from energy supplied by slow cooling and freezing of the liquid iron core. Core thermal history calculations have been hindered in the past by poor knowledge of the properties of iron alloys at the extreme pressures and temperatures pertaining in the core. This obstacle is now being overcome by developments in high pressure experiments and computational mineral physics. Here we review the relevant properties of iron alloys at core conditions and discuss their uncertainty and geophysical implications.Powerful constraints on core evolution are now possible, due partly to recent factor 2-3 upward revisions of the all-important electrical and thermal conductivities. This has dramatic implications for the thermal history of the entire Earth, not just the core: the inner core is very young, the core is cooling quickly, and was so hot in the past that the lowermost mantle

show abstract

mentioning

confidence: 89%

Section: Geophysical Implications Of Revised Core Propertiesmentioning

confidence: 99%

See 1 more Smart Citation

Constraints from material properties on the dynamics and evolution of Earth’s core

et al. 2015

View full text Add to dashboard Cite

show abstract

“…One way to infer sample geometry precisely after decompression is to use the resistance or heat capacity measurement itself and the known ambient pressure value of resistivity or specific heat, as in the high-pressure resistivity measurements of Ref. 34.…”

Section: Discussionmentioning

confidence: 99%

Modulation calorimetry in diamond anvil cells. I. Heat flow models

Geballe

Collins

Jeanloz

2017

Journal of Applied Physics

View full text Add to dashboard Cite

Numerical simulations of heat transport in diamond anvil cells reveal a possibility for absolute measurements of specific heat via high-frequency modulation calorimetry. Such experiments could reveal and help characterize temperature-driven phase transitions at high-pressure, such as melting, the glass transition, magnetic and electric orderings, or superconducting transitions. Specifically, we show that calorimetric information of a sample cannot be directly extracted from measurements at frequencies slower than the timescale of conduction to the diamond anvils (10s to 100s of kHz) since the experiment is far from adiabatic. At higher frequencies, laser-heating experiments allow relative calorimetric measurements, where changes in specific heat of the sample are discriminated from changes in other material properties by scanning the heating frequency from ∼ 1 MHz to 1 GHz. But laser-heating generates large temperature gradients in metal samples, preventing absolute heat capacities to be inferred. High-frequency Joule heating, on the other hand, allows accurate, absolute specific heat measurements if it can be performed at high-enough frequency: assuming a thin layer of KBr insulation, the specific heat of a 5 µm-thick metal sample heated at 100 kHz, 1 MHz, or 10 MHz frequency would be measured with 30%, 8% or 2% accuracy, respectively.

show abstract

“…In a telluric planet such as the Earth, the time-averaged electrical conductivity varies with the depth in the liquid core due to the increase of temperature and pressure [11]. However, one has to consider the effect of the convective temperature fluctuations which are quite smaller than the static radial variations.…”

Section: Arxiv:160400469v1 [Physicsflu-dyn] 2 Apr 2016mentioning

confidence: 99%

Fluctuations of Electrical Conductivity: A New Source for Astrophysical Magnetic Fields

Pétrélis¹,

Alexakis²,

Gissinger³

2016

Phys. Rev. Lett.

View full text Add to dashboard Cite

We consider the generation of magnetic field by the flow of a fluid for which the electrical conductivity is nonuniform. A new amplification mechanism is found which leads to dynamo action for flows much simpler than those considered so far. In particular, the fluctuations of the electrical conductivity provide a way to bypass anti-dynamo theorems. For astrophysical objects, we show through three-dimensional global numerical simulations that the temperature-driven fluctuations of the electrical conductivity can amplify an otherwise decaying large scale equatorial dipolar field. This effect could play a role for the generation of the unusually tilted magnetic field of the iced giants Neptune and Uranus. 45.70.Mg The current explanation for the existence of magnetic field in astrophysical objects was given in 1919 by Larmor [1]. The motion of an electrically conducting fluid amplifies a seed of magnetic field by induction: this is the dynamo instability. Despite nearly hundred years of research, several questions remain open. One of the reasons is that for a flow to be dynamo active, it has to be complex enough.For instance, for a fluid with uniform physical properties, planar flows cannot create magnetic fields [2]. This result together with other similar anti-dynamo theorems [3], severely constrain the structure of the flows that can act as dynamos. Broadly speaking, both the flow and the resulting magnetic field must be complex enough.In an astrophysical object, considering the electrical conductivity σ as a constant is a very crude simplification. In most natural situations (liquid core of planetary dynamos, plasmas of stellar convection zones, galaxies), the temperature T , the chemical compositions C i and the density of the fluid ρ are expected to display large variations. As a result the electrical conductivity of the fluid is unlikely to remain uniform in the bulk of the flow. In other words, σ , that is determined by ρ, T and C i can be written as a function of space and time σ (r,t) because ρ, T and C i are functions of space and time. The effect of a boundary of varying conductivity close to a flow tangent to the boundary had been considered to model inhomogeneities of the Earth mantle [4]. A dynamo instability has been predicted but requires a flow with a huge velocity [5]. In this article we describe how magnetic field generation is affected by conductivity variations in the bulk of the fluid.To calculate this effect, we have to take into account that σ depends on position in the equation for the magnetic field that readsInsight can be obtained using the approximation of scale separation. We assume that the velocity and conductivity fields are periodic of period l. We note · the spatial average over l. Let the magnetic diffusivity be η = (µ 0 σ ) −1 = η 0 + δ η, where η 0 is the mean of η and δ η its variations. We write B = B + b and consider that B varies on a very large scale compared to l. In this limit, B satisfies a mean-field (closed) equation that readswhere α B is the sum of two terms,Pr...

show abstract

The high conductivity of iron and thermal evolution of the Earth’s core

Cited by 270 publications

References 87 publications

Constraints from material properties on the dynamics and evolution of Earth’s core

Constraints from material properties on the dynamics and evolution of Earth’s core

Modulation calorimetry in diamond anvil cells. I. Heat flow models

Fluctuations of Electrical Conductivity: A New Source for Astrophysical Magnetic Fields

Contact Info

Product

Resources

About