Article
Geochemistry & Geophysics
Michael A. Calkins, Ryan J. Orvedahl, Nicholas A. Featherstone
Summary: The dynamics of convection-driven dynamos in a spherical shell, relevant to the geodynamo, were analyzed using numerical simulation data and asymptotic theory. The results showed that the Lorentz force is weaker than the mean buoyancy force across different Ekman numbers and thermal forcings, with a relative difference in forces of O(Ek(1/6)) within the investigated parameter space. The study also found that the mean zonal velocity scales as O(Ek(-1/3)), while the meridional circulation is asymptotically smaller by a factor of O(Ek(1/6)).
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
P. A. Davidson, A. Ranjan
Summary: Numerical simulations of the geodynamo show that the dynamo action is primarily driven by the effects of helicity, while differential rotation plays a secondary role. The simulations reveal several robust features, such as thin convective columns outside the tangent cylinder with a left-handed helicity in the north and right-handed helicity in the south, 2-D motion in the equatorial regions, positive radial current at mid-latitudes and negative radial current in the equatorial regions, radial outflow in the equatorial regions, and elevated temperatures near the equator. The high equatorial temperatures are a direct consequence of the skew-symmetric distribution of helicity, resulting in an anisotropic turbulent diffusion that preferentially carries heat radially outward along the equator.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Julien Aubert
Summary: Our understanding of the geodynamo has advanced recently thanks to improved geomagnetic data and realistic numerical simulations. Using a sequential, ensemble-based framework, high-resolution geomagnetic field models are assimilated into a numerical geodynamo simulation, resulting in an estimate of the present state and dynamics of Earth's core. The simulations accurately reproduce known features of the geodynamo, and the convective power is estimated at 2.95 +/- 0.2 TW. These physically realistic models allow for the study of deep Earth properties through geomagnetic data assimilation.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Astronomy & Astrophysics
V Skoutnev, J. Squire, A. Bhattacharjee
Summary: The study investigates the effects of stable stratification on mean-field dynamo theory, focusing on a non-helical large-scale dynamo (LSD) mechanism. The results show that the mechanism is robust to increasing stable stratification and capable of generating large-scale magnetic fields in stellar radiative zones.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Geochemistry & Geophysics
T. Schwaiger, T. Gastine, J. Aubert
Summary: This passage discusses the importance of measuring length scales with both energetic and dynamic relevance in fluid dynamics. It analyzes two length scales in magnetic and non-magnetic models that achieve this dual relevance, revealing different interpretations and misrepresentations of force balance. By focusing on these scales, the study uncovers insights into the underlying mechanisms of dynamo systems and their dominant length scales.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Astronomy & Astrophysics
A. Barik, S. A. Triana, M. Calkins, S. Stanley, J. Aurnou
Summary: This article studies convection in rotating spherical layers of fluid, focusing on the effect of the radius ratio of the spherical shell on critical quantities. By computing numerical results of critical quantities over a wide range of parameters, it is found that theoretical scaling laws can well explain these variations, but the radius ratio of the spherical shell also has an impact.
EARTH AND SPACE SCIENCE
(2023)
Article
Geochemistry & Geophysics
Julien Aubert, Nicolas Gillet
Summary: The study uses a geodynamo simulation model to analyze the interactions between slow convective motions and fast hydromagnetic waves in Earth's core, identifying three classes of fluid dynamic and hydromagnetic waves. These waves enrich and flatten the energy density spectrum of geomagnetic acceleration at decadal timescales, providing constraints on the observed frequency power spectrum.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Physics, Multidisciplinary
Lorenzo Sironi, Luca Comisso, Ryan Golant
Summary: We investigate the generation and amplification of magnetic fields through the Weibel instability in turbulent plasmas using kinetic particle-in-cell simulations. We find a relationship between the magnetic field strength and the turbulent velocity, as well as the relationship between the magnetic field energy and the turbulent kinetic energy. Our results suggest that turbulence can magnetize collisionless plasmas and create large-scale near-equipartition magnetic fields in the Universe.
PHYSICAL REVIEW LETTERS
(2023)
Article
Geochemistry & Geophysics
A. E. Stott, R. F. Garcia, A. Chedozeau, A. Spiga, N. Murdoch, B. Pinot, D. Mimoun, C. Charalambous, A. Horleston, S. D. King, T. Kawamura, N. Dahmen, S. Barkaoui, P. Lognonne, W. B. Banerdt
Summary: The SEIS experiment on the NASA InSight mission uses machine learning methods to analyze the relationship between weather data and seismic energy on Mars, detecting previously undetected marsquakes.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geochemistry & Geophysics
Julien Aubert, Philip W. Livermore, Christopher C. Finlay, Alexandre Fournier, Nicolas Gillet
Summary: By analyzing numerical geodynamo simulation and comparing with actual observations, it is found that geomagnetic jerks originate from the interaction between slow convection and rapid hydromagnetic wave propagation in the Earth's outer core. The simulation results support the hypothesis that the emission of magneto-inertial waves following a disruption of the leading-order force balance is the single physical root cause for jerks observed throughout the geomagnetic record.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
Irene Bonati, Marine Lasbleis, Lena Noack
Summary: Research shows that the iron content of planets has a significant impact on core structure, evolution, and magnetic field lifetimes. Planets with high iron content may develop large solid inner cores, while massive planets with intermediate iron inventories have the longest dynamo lifetimes.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2021)
Article
Geochemistry & Geophysics
M. Puica, V Dehant, M. Folgueira, T. Van Hoolst, J. Rekier
Summary: The Earth's rotation is affected by gravitational torques from the Sun and the Moon, as well as angular momentum exchange with the atmosphere and hydrosphere. This study focuses on the influence of topography at the core-mantle boundary on variations in the length-of-day (LOD). Using an analytical approach, the researchers identify resonance frequencies and degrees of topographic coefficients that amplify tidal effects on LOD variations.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2023)
Article
Geosciences, Multidisciplinary
C. A. Denton, A. R. Rhoden
Summary: This article investigates the geology and internal evolution of Mimas, revealing the possibility of a liquid ocean and studying the formation of its major impact basin through simulations.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
C. Adeene Denton, Brandon C. Johnson, Shigeru Wakita, Andrew M. Freed, H. Jay Melosh, S. Alan Stern
Summary: Through simulating the impact that formed Sputnik Planitia, it was found that Pluto's interior may have included a subsurface ocean over 150 km thick and a hydrated core at the time of impact. The observed lineations antipodal to Sputnik Planitia may have been caused by significant deformation resulting from the impact.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Geochemistry & Geophysics
Christopher J. Davies, Richard K. Bono, Domenico G. Meduri, Julien Aubert, Samuel Greenwood, Andrew J. Biggin
Summary: The researchers investigate the variation of Earth's magnetic field strength over geological time by combining numerical geodynamo simulations with theoretical scaling laws. They find that both scaling laws, despite uncertainties from different heating modes and boundary conditions, are compatible with the power-law behavior exhibited by the internal field and core-mantle boundary fields. The QG-MAC-free scaling matches Earth's modern CMB field, while the QG-MAC-fixed prediction overestimates palaeointensities over the last 3.5 Gyr.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Editorial Material
Astronomy & Astrophysics
ZhenLiang Tian, Maria T. Zuber, Sabine Stanley
Article
Multidisciplinary Sciences
Jerry X. Mitrovica, Carling C. Hay, Eric Morrow, Robert E. Kopp, Mathieu Dumberry, Sabine Stanley
Article
Geochemistry & Geophysics
Hiroaki Matsui, Eric Heien, Julien Aubert, Jonathan M. Aurnou, Margaret Avery, Ben Brown, Bruce A. Buffett, Friedrich Busse, Ulrich R. Christensen, Christopher J. Davies, Nicholas Featherstone, Thomas Gastine, Gary A. Glatzmaier, David Gubbins, Jean-Luc Guermond, Yoshi-Yuki Hayashi, Rainer Hollerbach, Lorraine J. Hwang, Andrew Jackson, Chris A. Jones, Weiyuan Jiang, Louise H. Kellogg, Weijia Kuang, Maylis Landeau, Philippe Marti, Peter Olson, Adolfo Ribeiro, Youhei Sasaki, Nathanael Schaeffer, Radostin D. Simitev, Andrey Sheyko, Luis Silva, Sabine Stanley, Futoshi Takahashi, Shin-ichi Takehiro, Johannes Wicht, Ashley P. Willis
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
(2016)
Article
Geochemistry & Geophysics
S. Stanley, J. Bloxham
PHYSICS OF THE EARTH AND PLANETARY INTERIORS
(2016)
Article
Geochemistry & Geophysics
N. Urbancic, R. Ghent, C. L. Johnson, S. Stanley, D. Hatch, K. A. Carroll, W. B. Garry, M. Talwani
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2017)
Article
Astronomy & Astrophysics
Bob Yunsheng Tian, Sabine Stanley
ASTROPHYSICAL JOURNAL
(2013)
Article
Geochemistry & Geophysics
N. -H. Chan, J. X. Mitrovica, A. Daradich, J. R. Creveling, I. Matsuyama, S. Stanley
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2014)
Article
Geosciences, Multidisciplinary
C. Yan, S. Stanley
GEOPHYSICAL RESEARCH LETTERS
(2018)
Editorial Material
Geochemistry & Geophysics
Steven A. Hauck, David Baratoux, Sabine Stanley
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2019)
Editorial Material
Geochemistry & Geophysics
Laurent G. J. Montesi, Steven A. Hauck, David Baratoux, Anni Maattanen, A. Deanne Rogers, Sabine Stanley
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2020)
Article
Geochemistry & Geophysics
Brian J. Anderson, Regupathi Angappan, Ankit Barik, Sarah K. Vines, Sabine Stanley, Pietro N. Bernasconi, Haje Korth, Robin J. Barnes
Summary: The study assesses the use of Iridium Communications magnetometer data for Earth's magnetic field characterization from 2010 to 2015. Residuals between the data and IGRF-11 show consistent patterns evolving gradually over the years. Spherical harmonic coefficients computed for each quiet day help identify artifacts at orbit precession and seasonal periods, which are then removed by notch filtering.
GEOCHEMISTRY GEOPHYSICS GEOSYSTEMS
(2021)
Article
Geochemistry & Geophysics
K. M. Moore, A. Barik, S. Stanley, D. J. Stevenson, N. Nettelmann, R. Helled, T. Guillot, B. Militzer, S. Bolton
Summary: Understanding the interior structure of Jupiter is crucial for studying planetary accretion models. Recent findings suggest the presence of stable stratification in the form of an upper layer and a potentially stratified dilute core within the planet. However, the equations of state for hydrogen and helium remain uncertain. In this study, high-resolution numerical magnetohydrodynamic simulations of Jupiter's magnetic field are used to constrain the extent of stable stratification. The results indicate that an upper stably stratified layer helps explain Jupiter's magnetic field and winds, while an entirely stably stratified dilute core yields worse fits. These findings suggest that alternative modalities may be required if a dilute core is present.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2022)
Article
Geosciences, Multidisciplinary
C. Yan, S. Stanley
Summary: The study reveals that the characteristics of Saturn's magnetic field are sensitive to the properties of a stably stratified helium rain-out layer and thermal perturbations at the top of the layer.
Article
Astronomy & Astrophysics
Konstantin Batygin, Sabine Stanley
ASTROPHYSICAL JOURNAL
(2014)