Article
Physics, Multidisciplinary
Federico Pizzi, Andre Giesecke, Jan Simkanin, Frank Stefani
Summary: The study reveals that there are sharp transitions in flow states between prograde precession and retrograde precession, with the former showing abrupt breakdown of flow excited by the forcing mechanism. Additionally, prograde and perpendicular precession lead to a smooth transition between low and high flow states, while retrograde precession does not exhibit this behavior.
NEW JOURNAL OF PHYSICS
(2021)
Article
Geosciences, Multidisciplinary
David Gubbins, Yi Jiang, Simon E. Williams, Keke Zhang
Summary: Mars has a magnetic field originating in its strongly magnetized crust. The decomposition of simple candidate magnetic structures helps separate the responsible parts for anomalies from those that are invisible. A uniform magnetic layer does not produce anomalies, while secondary magnetization may reflect the primordial dynamo field. A magnetized crust with variable thickness can produce large anomalies, but they are absent if the magnetic layer lies deeper than the crater floor.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Astronomy & Astrophysics
Bruce G. Bills, Bryan R. Scott
Summary: The primary objective of this study is to develop and present improved models of the rotational motions of the Galilean satellites. The models include both precessions and nutations of the spin poles, and forced librational oscillations of the rotation rates. Current measurements and models are limited, but future missions are expected to provide better data.
PLANETARY AND SPACE SCIENCE
(2022)
Article
Geosciences, Multidisciplinary
A. AlHantoobi, J. Buz, J. G. O'Rourke, B. Langlais, C. S. Edwards
Summary: Martian crust shows strong magnetic anomalies, which are not well explained yet. Research suggests a relationship between crustal magnetization and composition, with specific absorption features contributing to the variance. Further investigation is needed to understand the geological magnetic field changes on Mars.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Astronomy & Astrophysics
Bo-Sheng Li, Xi-Yun Hou
Summary: A novel algorithm based on the Lindstedt-Poincare method is proposed to construct an analytical solution of the lunar orbit. A numerical fitting algorithm is used to improve the accuracy of the solution within 20 years. It also provides a general way to treat the third-body perturbation in rectangular coordinates.
ASTRONOMICAL JOURNAL
(2023)
Article
Geosciences, Multidisciplinary
S. M. Tikoo, J. Jung
Summary: This study tested whether lunar samples could have been magnetized during return to Earth, sample handling, or transport. The results showed that high coercivity magnetizations observed within lunar rocks are generally not magnetic contamination and were initially acquired on the Moon.
GEOPHYSICAL RESEARCH LETTERS
(2023)
Article
Multidisciplinary Sciences
Wanying Kang, Tushar Mittal, Suyash Bire, Jean-Michel Campin, John Marshall
Summary: The study reveals the significant impact of salinity and heat distribution within the subsurface ocean of Enceladus on the geometry of its ice shell, investigating the driving mechanisms of ocean circulation by heat and salt exchange, and the key factors affecting the equilibrium state of the ice shell.
Article
Geochemistry & Geophysics
Dexin Lai, Tao Li
Summary: Planetary waves in Venus's atmosphere and their long-term variations are studied using LIR observations and cloud-tracking wind fields. The dominant wave is a wavenumber 1 wave with a period of 5-6 days (QFDW), symmetrically distributed in the midlatitudes of both hemispheres. The wave's phase speed is close to the background zonal wind, indicating the possible existence of a critical level near 65 km altitude.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2023)
Article
Geosciences, Multidisciplinary
A. Mittelholz, C. L. Johnson, M. Fillingim, S. P. Joy, J. Espley, J. Halekas, S. Smrekar, W. B. Banerdt
Summary: Solar activity, such as coronal mass ejections and corotating interaction regions, affects the solar wind which interacts with the magnetic fields of planets. In December 2020, the InSight mission's magnetometer observed increased solar activity, leading to magnetic field fluctuations. This observation on Mars demonstrates how solar activity can alter magnetic fields at the surface.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Geochemistry & Geophysics
B. E. Strauss, S. M. Tikoo, J. Gross, J. B. Setera, B. Turrin
Summary: Recent paleomagnetic studies indicate that the Moon's magnetic field peaked around 3.56 billion years ago and then declined, with limited samples showing this decline. Analysis of three lunar basalt samples suggests that they were not magnetized in conditions with a magnetic field exceeding 4-7 mu T during their formation. The updated radiometric ages support a constraint of the lunar field intensity to around 3.1 billion years ago, confirming a dramatic change in the mechanism of lunar dynamo generation between 3.6 and 3.1 billion years ago.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2021)
Article
Geochemistry & Geophysics
H. C. F. C. Hay, I. Matsuyama, R. T. Pappalardo
Summary: This article investigates the tidal response model of Europa and Ganymede, considering ocean dynamics and the coupling effect with the ice shell. High-frequency tidal deformation is resonantly amplified by ocean dynamics, providing a unique determination of ocean thickness. This study is of great importance for understanding the thermal/orbital evolution of the moons.
JOURNAL OF GEOPHYSICAL RESEARCH-PLANETS
(2022)
Article
Geochemistry & Geophysics
R. D. Ray, J. -P. Boy, B. K. Arbic, G. D. Egbert, S. Y. Erofeeva, L. Petrov, J. F. Shriver
Summary: Studying earth tides requires filtering out effects from ocean tides, which have small amplitudes and pose modeling challenges. Numerical simulations must take into account various potential influences.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2021)
Article
Geochemistry & Geophysics
D. Melini, C. Saliby, G. Spada
Summary: This paper revisits the computation of Love numbers for a spherically symmetric viscoelastic Earth, presenting a numerical evaluation method based on Laplace inversion and complex-valued frequency-dependent Love numbers. The implementation is done in the ALMA(3) program, allowing for the computation of Love numbers for planetary bodies with various rheological profiles.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
Article
Geochemistry & Geophysics
L. Sachl, J. Velimsky, J. Fullea, Z. Martinec
Summary: In this paper, a new approach to the inverse problem of global electromagnetic induction is developed and tested, aiming to retrieve the 3-D structure of electrical conductivity in the suboceanic upper mantle using satellite-observed tidal magnetic field. Parametric studies and synthetic tests demonstrate the successful reconstruction of suboceanic upper mantle conductivity structure, with correlation coefficient greater than 0.8 in the ideal noise-free case.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
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
Michael Le Bars, Ankit Barik, Fabian Burmann, Daniel P. Lathrop, Jerome Noir, Nathanael Schaeffer, Santiago A. Triana
Summary: Understanding fluid flows in planetary cores and subsurface oceans, as well as their signatures in available observational data, is a challenging interdisciplinary task that requires a combination of experimental, theoretical, and numerical approaches to better understand the dynamics of planetary interior flows driven by mechanical forcing.
SURVEYS IN GEOPHYSICS
(2022)
Article
Mechanics
Jiyang He, Benjamin Favier, Michel Rieutord, Stephane Le Dizes
Summary: This study examines the internal shear layers generated by the longitudinal libration of the inner core in a rotating spherical shell. By using asymptotic and numerical analysis, the researchers provide insights into the behavior of these shear layers and compare the asymptotic predictions with direct numerical results. The study demonstrates that, with decreasing Ekman numbers, the agreement between the asymptotic predictions and numerical results improves.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Physics, Multidisciplinary
Remi Monthiller, Aurore Loisy, Mimi A. R. Koehl, Benjamin Favier, Christophe Eloy
Summary: In marine plankton, certain swimming species can perceive their environment with flow sensors. This study suggests that these organisms can navigate faster in turbulence by utilizing flow information and choosing swimming directions according to local flow gradients.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
D. Lemasquerier, B. Favier, M. Le Bars
Summary: This study presents experimental results from a laboratory analog of zonal jets in deep gas giants. The researchers found that turbulent zonal jets can spontaneously emerge and reach equilibrium in the experiments, with up to 70% of the total kinetic energy of the flow. They also validated the zonostrophic theory in a fully three-dimensional framework. Additionally, they quantified the mixing of potential vorticity in the flow and showed that it can be estimated using the Thorpe scale.
Article
Physics, Fluids & Plasmas
Quentin Kriaa, Eliot Subra, Benjamin Favier, Michael Le Bars
Summary: We experimentally investigated the behavior of heavy particles released as turbulent clouds in quiescent water, with and without background rotation. Our systematic experiments explored various rotation rates and particle sizes, and showed that the behavior of particle clouds differs from salt-water thermals due to the particulate nature of the turbulence forcing. In the absence of rotation, particle clouds initially behave similarly to salt-water thermals, but their entrainment capacity is modulated by particle effects. However, this behavior is limited in time due to the decoupling between turbulent eddies and particles. In the presence of rotation, the cloud's expansion is interrupted by the Coriolis force, leading to the formation of vortical columnar flows and increased particle residence time.
PHYSICAL REVIEW FLUIDS
(2022)
Article
Mechanics
T. W. Christopher, M. Le Bars, Stefan Llewellyn G. Smith
Summary: Linear and nonlinear stability analyses are performed to determine the critical Rayleigh numbers for a Rayleigh-Benard convection configuration with time-varying bottom boundary heat flux. The linear stability Ra(cr) is generally higher than the nonlinear stability Ra-cr, and the domain for subcritical instability becomes larger with increasing frequency and decreasing Prandtl number. These results are confirmed by direct numerical simulations.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Michael Le Bars
Summary: Despite ongoing debates, the study on wave turbulence and its scale transfers is challenging due to experimental and numerical difficulties. The numerical study of Thomas & Ding sheds new light on the upscale transfer of waves in rotating shallow water equations and highlights weaknesses in the theoretical foundations. This work calls for improved modeling and has implications for understanding large-scale climatic features.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
J. Labarbe, P. Le Gal, U. Harlander, S. Le Dizes, B. Favier
Summary: This paper presents a numerical analysis of the instability in horizontally sheared Poiseuille flow with vertical stratification. The study extends the previous work on the linear instability of this configuration and investigates nonlinear regimes through direct numerical simulations. The results show that the flow loses its vertical homogeneity through a secondary bifurcation and exhibits intermittent dynamics with bursting events and localized shear instabilities.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Physics, Multidisciplinary
Louise Terrien, Benjamin Favier, Edgar Knobloch
Summary: The heat transport in rapidly rotating Rayleigh-Benard convection is crucial for many geophysical flows. However, laboratory measurements are hindered by the development of strong wall modes along the vertical walls, which significantly disturb the heat flux. In this study, we demonstrate that narrow horizontal fins along the vertical walls effectively suppress the wall modes, ensuring their contribution to the global heat flux is negligible. This opens the door for new experimental studies on geophysically relevant regimes of rotating convection.
PHYSICAL REVIEW LETTERS
(2023)
Article
Physics, Fluids & Plasmas
Quentin Kriaa, Benjamin Favier, Michael Le Bars
Summary: By numerically modeling settling clouds created by instantaneous releases of heavy particles, we confirmed the maximum growth rate of clouds with a finite Rouse number of 0.22. Our simulations also validated the use of a one-fluid two-way coupling numerical model to simulate particle clouds with weak particle inertia.
PHYSICAL REVIEW FLUIDS
(2023)
Article
Geochemistry & Geophysics
M. Bouffard, B. Favier, D. Lecoanet, M. Le Bars
Summary: Seismic and magnetic observations suggest the presence of a stably stratified layer atop Earth's core, which may impact the morphology of the geomagnetic field and the evolution of the core. This study focuses on internal gravity waves (IGW) in stratified layers, finding that energy distribution depends on the Prandtl number and the mean kinetic energy in the layer is about 0.1 percent that of the convective region in the absence of rotational and magnetic effects.
GEOPHYSICAL JOURNAL INTERNATIONAL
(2022)
