scholarly journals A simple 3-D numerical model of thermal convection in Earth's growing inner core: on the possibility of the formation of the degree-one structure with lateral viscosity variations

2015 ◽  
Vol 7 (4) ◽  
pp. 3817-3841
Author(s):  
M. Yoshida
Keyword(s):  
Thermal Convection ◽  
Inner Core ◽  
Outer Core ◽  
Limited Range ◽  
Asymmetric Structure ◽  
Planetary Scale ◽  
Core Boundary ◽  
Earth’S Inner Core ◽  
East West ◽  
Rheological Heterogeneity

Abstract. An east-west hemispherically asymmetric structure for Earth's inner core has been suggested by various seismological evidence, but its origin is not clearly understood. Here, to investigate the possibility of an "endogenic origin" for the degree-one thermal/mechanical structure of the inner core, I performed new numerical simulations of thermal convection in the growing inner core. A setup value that controls the viscosity contrast between the inner core boundary and the interior of the inner core, ΔηT, was taken as a free parameter. Results show that the degree-one structure only appeared for a limited range of ΔηT; such a scenario may be possible but is not considered probable for the real Earth. The degree-one structure may have been realized by an "exogenous factor" due to the planetary-scale thermal coupling among the lower mantle, the outer core, and the inner core, not by an endogenic factor due to the internal rheological heterogeneity.

Measuring the melting curve of iron at super-Earth core conditions

Science ◽  
2022 ◽  
Vol 375 (6577) ◽  
pp. 202-205
Author(s):  
Richard G. Kraus ◽  
Russell J. Hemley ◽  
Suzanne J. Ali ◽  
Jonathan L. Belof ◽  
Lorin X. Benedict ◽  
...  
Keyword(s):  
Liquid Metal ◽  
Inner Core ◽  
Melting Curve ◽  
Radiation Shielding ◽  
Metal Core ◽  
Earth Core ◽  
Core Boundary ◽  
Earth Like Planets ◽  
Earth’S Inner Core ◽  
Core Conditions

Terapascal iron-melting temperature The pressure and temperature conditions at which iron melts are important for terrestrial planets because they determine the size of the liquid metal core, an important factor for understanding the potential for generating a radiation-shielding magnetic field. Kraus et al . used laser-driven shock to determine the iron-melt curve up to a pressure of 1000 gigapascals (see the Perspective by Zhang and Lin). This value is about three times that of the Earth’s inner core boundary. The authors found that the liquid metal core lasted the longest for Earth-like planets four to six times larger in mass than the Earth. —BG

Revised velocities in the Earth's core

1973 ◽  
Vol 63 (3) ◽  
pp. 1073-1105 ◽  
Author(s):  
Anthony Qamar
Keyword(s):  
Transition Zone ◽  
Inner Core ◽  
Velocity Model ◽  
Outer Core ◽  
Travel Times ◽  
Zone Boundary ◽  
Underground Nuclear Explosions ◽  
Nuclear Explosions ◽  
Core Boundary ◽  
Velocity Jump

abstract Travel times and amplitudes of PKP and PKKP from three earthquakes and four underground nuclear explosions are presented. Observations of reflected core waves at nearly normal angles of incidence provide new constraints on the average velocities in the inner and outer core. Interpretation of these data suggests that several small but significant changes to Bolt's (1962) core velocity model (T2) are necessary. A revised velocity model KOR5 is given together with the derived travel times that are consistent with the 1968 tables for P. Model KOR5 possesses a velocity in the transition zone which is 112 per cent lower than that in model T2. In addition, KOR5 has a velocity jump at the transition zone boundary (r = 1782 km) of 0.013 km/sec and a jump at the inner core boundary (r = 1213 km) of 0.6 km/sec. These values are, respectively, 1/20 and 2/3 of the corresponding model T2 values.

scholarly journals On shear wave velocity in the top of the Earth’s inner core

2019 ◽  
Vol 488 (4) ◽  
pp. 434-438
Author(s):  
D. N. Krasnoshchekov ◽  
V. M. Ovtchinnikov ◽  
O. A. Usoltseva
Keyword(s):  
Shear Wave ◽  
Wave Velocity ◽  
Shear Wave Velocity ◽  
Inner Core ◽  
Solid Core ◽  
The Earth ◽  
Inner Surface ◽  
Core Boundary ◽  
Standard Models ◽  
Earth’S Inner Core

Analysis of PKIIKP waves reflected off the inner surface of the solid core boundary and recorded close to the antipode indicates the shear wave velocity in its top can be by 10-60% below 3.5 km/s envisaged by standard models of the Earth.

scholarly journals Fe Alloy Slurry and a Compacting Cumulate Pile Across Earth's Inner‐Core Boundary

2019 ◽  
Vol 124 (11) ◽  
pp. 10954-10967 ◽  
Author(s):  
Youjun Zhang ◽  
Peter Nelson ◽  
Nick Dygert ◽  
Jung‐Fu Lin
Keyword(s):  
Inner Core ◽  
Core Boundary ◽  
Earth’S Inner Core

Shear Properties of Earth's Inner Core

2021 ◽  
Vol 50 (1) ◽  
Author(s):  
Hrvoje Tkalčić ◽  
Sheng Wang ◽  
Thanh-Son Phạm
Keyword(s):  
Shear Wave ◽  
Inner Core ◽  
Normal Modes ◽  
Outer Core ◽  
Annual Review ◽  
Publication Date ◽  
Shear Properties ◽  
Shear Wave Speed ◽  
Earth’S Inner Core ◽  
Shear Structure

Understanding how Earth's inner core (IC) develops and evolves, including fine details of its structure and energy exchange across the boundary with the liquid outer core, helps us constrain its age, relationship with the planetary differentiation, and other significant global events throughout Earth's history, as well as the changing magnetic field. Since its discovery in 1936 and the solidity hypothesis in 1940, Earth's IC has never ceased to inspire geoscientists. However, while there are many seismological observations of compressional waves and normal modes sensitive to the IC's compressional and shear structure, the shear waves that provide direct evidence for the IC's solidity have remained elusive and have been reported in only a few publications. Further advances in the emerging correlation-wavefield paradigm, which explores waveform similarities, may hold the keys to refined measurements of all inner-core shear properties, informing dynamical models and strengthening interpretations of the IC's anisotropic structure and viscosity. ▪ What are the shear properties of the inner core, such as the shear-wave speed, shear modulus, shear attenuation, and shear-wave anisotropy? Can the shear properties be measured seismologically and confirmed experimentally? Expected final online publication date for the Annual Review of Earth and Planetary Sciences, Volume 50 is May 2022. Please see http://www.annualreviews.org/page/journal/pubdates for revised estimates.

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