Article
Physics, Fluids & Plasmas
Nelson Poumaere, Benoit Pier, Florence Raynal
Summary: We investigate the distributions of residence time for in-line chaotic mixers and find that they all possess a t(-3) tail, significantly different from Gaussian distribution. We propose a new measure, mean absolute deviation, for the width of the distribution, and show its convergence in the limit of large sample size. Additionally, we analyze the performance of different in-line mixers in terms of residence time when varying the number of elements and the shape of the cross section.
Article
Geochemistry & Geophysics
V Lesur, N. Gillet, M. D. Hammer, M. Mandea
Summary: This paragraph discusses the evidence of fast variations in the Earth's core field observed in magnetic observatory and satellite records. It explains how these variations are identified at the Earth's surface and characterized by satellite data. The paragraph also mentions the extraction of their properties at the core mantle boundary through localized and global modeling processes, with emphasis on their time scales. Finally, it lists the possible types of waves in the liquid outer core that may cause these observed fast variations.
SURVEYS IN GEOPHYSICS
(2022)
Article
Geosciences, Multidisciplinary
R. M. Blangsboll, C. C. Finlay, C. Kloss
Summary: The 1969 geomagnetic impulse provided evidence for rapid changes in Earth's core-generated magnetic field, which were likely caused by localized variations at the core-mantle boundary. Similar impulses were observed in 2017, with distinctive enhancements in secular variation leading up to the 1969 event.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Multidisciplinary Sciences
Matthew Maitra, Jiawen Luo, Andrew Jackson
Summary: This paper investigates the canonical problem of magnetic field decay in an electrically conducting fluid ball. The problem is closely related to the decay modes of a rigid ball, and the spatial form of the eigenmodes remains mostly unchanged. The decaying but oscillatory behavior of the new fluid eigenmodes, known as quasi-free-decay (QFD) modes, is derived using perturbation methods in the case of rapid rotation and a static applied background magnetic field. The results are in good agreement with numerical calculations, even for moderate values of the Elsasser number lambda.
PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2023)
Article
Physics, Fluids & Plasmas
Ying Chen, Zhenhua Chai, Baochang Shi
Summary: In this paper, a fourth-order multiple-relaxation-time lattice Boltzmann (MRT-LB) model is developed for the one-dimensional convection-diffusion equation (CDE) with constant velocity and diffusion coefficient, using the D1Q3 lattice structure. The Chapman-Enskog analysis is performed to recover the CDE from the MRT-LB model. An explicit four-level finite-difference (FLFD) scheme is derived from the MRT-LB model for the CDE, and the truncation error of the FLFD scheme is obtained through Taylor expansion, showing fourth-order accuracy in space at the diffusive scaling. Stability analysis is presented, and the same stability condition is derived for the MRT-LB model and FLFD scheme. Numerical experiments are conducted to test the MRT-LB model and FLFD scheme, which demonstrate a fourth-order convergence rate in space, consistent with the theoretical analysis.
Article
Mechanics
Lukas Babor, Hendrik C. Kuhlmann
Summary: This study investigates the Lagrangian transport in the laminar incompressible flow in a two-dimensional square cavity driven by a harmonic tangential oscillation of the lid, covering a wide range of Reynolds and Strouhal numbers. The topology of fluid trajectories is analyzed by stroboscopic projections, revealing the co-existence of chaotic trajectories and regular Kolmogorov-Arnold-Moser (KAM) tori. The structure of pathlines strongly depends on the Reynolds number and the oscillation frequency of the lid.
Article
Mechanics
Haotian Wu, Francesco Romano, Hendrik C. Kuhlmann
Summary: Experimental investigation reveals that in a two-sided lid-driven cavity, particle motion is influenced by convection cells, KAM tori, and wall effects to form attractors. In cases where there is a deviation between particle density and fluid density, inertial attractors are created.
JOURNAL OF FLUID MECHANICS
(2021)
Article
Mechanics
Haotian Wu, Francesco Romano, Hendrik C. Kuhlmann
Summary: The motion of finite-size particles in the cuboidal lid-driven cavity flow is experimentally investigated for Reynolds numbers 100 and 200. The steady three-dimensional flows exhibit chaotic and regular streamlines, with the latter confined to Kolmogorov-Arnold-Moser (KAM) tori. The interaction between the moving wall and the particle creates global particle attractors. For neutrally buoyant particles, these attractors are periodic or quasi-periodic, strongly attracting, and located in or near KAM tori. As density mismatch between particle and fluid increases, buoyancy and inertia become important, causing the attractors to change in shape, position, and attraction rates.
JOURNAL OF FLUID MECHANICS
(2023)
Article
Mechanics
Ahad Izadi, Ali Mohebbi, Amir Ehsan Feili Monfared
Summary: This study proposes a new method based on scalar diffusion phenomenon combined with lattice Boltzmann method to calculate normal vectors in simulating two-phase flows. The proposed method is more accurate and computationally efficient compared to standard methods such as Youngs, ELVIRA, Swartz, and VOSET. It is also less affected by the gap between neighboring obstacles in multi-obstacle media.
Article
Agronomy
Oluwakemi Dare-Idowu, Aurore Brut, Joan Cuxart, Tiphaine Tallec, Vincent Rivalland, Bartosz Zawilski, Eric Ceschia, Lionel Jarlan
Summary: This study analyzed the impact of different vegetation types and climatic variables on energy balance closure and flux partitioning using a unique database of EC flux measurements in two agricultural sites in southwestern France. The results indicated that site location had a stronger effect on energy balance closure than crop type and stage, while rainfall and phenological stages were found to influence energy partitioning.
AGRICULTURAL AND FOREST METEOROLOGY
(2021)
Article
Multidisciplinary Sciences
Andreas Nilsson, Neil Suttie, Joseph S. Stoner, Raimund Muscheler
Summary: The strength of the Earth's magnetic field has rapidly decreased over the past two centuries, coinciding with the growth of the South Atlantic Anomaly, leading to speculation about a field reversal. Through indirect observations over the past 9,000 years, evidence of recurrent hemispherical field asymmetries related to millennial-scale variations in the dipole moment has been identified, suggesting potential ancient analogs.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2022)
Article
Engineering, Marine
Qian-yi Chen, Yan-ping He, Ting Xiong, Ming-zhi Li, Wei-huang Liu
Summary: Trailing suction hopper dredgers (TSHDs) are the main type of ships used for dredging projects. This study investigates the advection and diffusion process of the overflow near the hull using numerical simulations. It is found that the overflow regimes are influenced by the Richardson numbers and velocity ratios. Additionally, the hull structure and the propeller contribute to the turbulence in the flow field, and external conditions have a more pronounced effect on the overflow at low towing speeds.
Article
Geosciences, Multidisciplinary
E. Thebault, G. Hulot, B. Langlais, P. Vigneron
Summary: The detailed mapping of Earth's magnetic field, using satellite and near-surface measurements, has produced a global model with SH degree 1050 that is in agreement with previous satellite-based models at large wavelengths. The model is stable when downward continued to the Earth's surface and fits the CHAMP and Swarm satellite data down to expected noise levels.
GEOPHYSICAL RESEARCH LETTERS
(2021)
Article
Agronomy
Mary Rose Mangan, Oscar Hartogensis, Aaron Boone, Oliver Branch, Guylaine Canut, Joan Cuxart, Hugo J. de Boer, Michel Le Page, Daniel Martinez-Villagrasa, Josep Ramon Miro, Jeremy Price, Jordi Vila-Guerau de Arellano
Summary: Irrigation in semi-arid regions induces thermal heterogeneity at different spatial scales, affecting surface energy partitioning, atmospheric boundary layer development, and atmosphere-surface interactions. This study investigates the role of irrigation-induced thermal heterogeneity scales on surface fluxes and diurnal convective boundary layer development using data from the LIAISE experiment and a land-atmosphere model. The observed surface heterogeneity is characterized by Bowen ratios ranging from -0.01 in irrigated areas to -30 in non-irrigated areas. The study finds that surface fluxes and boundary layer dynamics are influenced by spatial scale and non-local processes such as advection play a significant role in energy partitioning at the local scale.
AGRICULTURAL AND FOREST METEOROLOGY
(2023)
Article
Mechanics
Rahul Kumar Mondal, Parmod Kumar
Summary: This study experimentally investigates the formation of pump-induced vortices and the subsequent entrainment of air. The vortex profiles are categorized based on their behaviors, and the entrained air changes from discrete bubbles to a continuous gaseous core. The rate of the vortex tip's traversal depends on its location, and the use of an air separator system reduces flow fluctuations.
Article
Astronomy & Astrophysics
J. Hubert, C. D. Beggan, G. S. Richardson, T. Martyn, A. W. P. Thomson
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2020)
Article
Astronomy & Astrophysics
T. Divett, D. H. Mac Manus, G. S. Richardson, C. D. Beggan, C. J. Rodger, M. Ingham, E. Clarke, A. W. P. Thomson, M. Dalzell, Y. Obana
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2020)
Article
Computer Science, Interdisciplinary Applications
Paolo Marangio, Vyron Christodoulou, Rosa Filgueira, Hannah F. Rogers, Ciaran D. Beggan
COMPUTERS & GEOSCIENCES
(2020)
Article
Meteorology & Atmospheric Sciences
E. Williams, T. Bozoki, G. Satori, C. Price, P. Steinbach, A. Guha, Y. Liu, C. D. Beggan, M. Neska, R. Boldi, M. Atkinson
Summary: The study reveals that there was a significant increase in Schumann resonance intensity before two super El Nino events in 1997/98 and 2015/16, indicating a precursor for extreme climate events. Multistation observations from different years show that increased lightning activity mainly occurred in different regions, and the variations in SR intensity may be related to extremes in global surface air temperature.
JOURNAL OF GEOPHYSICAL RESEARCH-ATMOSPHERES
(2021)
Article
Geosciences, Multidisciplinary
William J. Brown, Ciaran D. Beggan, Grace A. Cox, Susan Macmillan
Summary: The British Geological Survey submitted three candidate models for the 13th generation International Geomagnetic Reference Field, derived from data collected by European Space Agency Swarm satellites and ground observatories between 2013.9 and 2019.7. These models include time dependence for both internal and external fields, with predictions for magnetic field secular variation from 2020 to 2025.
EARTH PLANETS AND SPACE
(2021)
Article
Astronomy & Astrophysics
L. Orr, S. C. Chapman, C. D. Beggan
Summary: The study uses Haar wavelet transform to localize the storm-time response in European ground-based magnetometer measurements and modeled geomagnetically induced currents in the high voltage grid of Great Britain. By analyzing the wavelet cross-correlation of GIC in the grounded nodes, a time-varying network of GIC flow around the GB grid during storms was built, revealing highly intermittent long-range coherent responses and spatial patterns that do not simply follow the rate of change of the magnetic field.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2021)
Article
Ecology
Fernando Benitez-Paez, Vanessa da Silva Brum-Bastos, Ciaran D. Beggan, Jed A. Long, Urska Demsar
Summary: This study explores how migratory animals use geomagnetic information for navigation, focusing on the merging of satellite geomagnetic data with animal tracking data. By developing a new tool for data fusion, researchers can access accurate real-time satellite geomagnetic data during animal tracking studies, providing insights for large-scale multi-species migratory studies. The tool has the potential to uncover new knowledge about geomagnetic navigation and resolve long-standing debates in the field.
Article
Astronomy & Astrophysics
C. Haines, M. J. Owens, L. Barnard, M. Lockwood, C. D. Beggan, A. W. P. Thomson, N. C. Rogers
Summary: In this paper, a method is presented to temporally downscale low-resolution magnetic field data to improve subsequent geoelectric field magnitude estimates, outperforming the linear-interpolation approach. By using analogous ensemble (AnEn) method to predict geomagnetically induced currents (GIC), it is demonstrated that the proposed method can accurately drive an impacts model and improve forecasting capability.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2022)
Article
Astronomy & Astrophysics
R. L. Bailey, R. Leonhardt, C. Moestl, C. Beggan, M. A. Reiss, A. Bhaskar, A. J. Weiss
Summary: The forecasting of local GIC effects has been mostly based on the proxy forecasting of dB/dt, and little attention has been given to directly forecasting geoelectric fields or GICs themselves. In this study, machine learning tools, specifically recurrent neural networks or LSTMs, are employed to predict geoelectric fields and GICs using solar wind observations as input. The results show that the LSTM model performs better in predicting GICs when trained on specific substation values, but only a fraction of the largest GICs are correctly predicted. The model has a correlation of around 0.6 with measurements and a root-mean-square error of 0.7 A. The probability of detecting mild activity in GICs is approximately 50%, while it is 15% for larger GICs.
SPACE WEATHER-THE INTERNATIONAL JOURNAL OF RESEARCH AND APPLICATIONS
(2022)
Review
Multidisciplinary Sciences
Juliet Biggs, Atalay Ayele, Tobias P. Fischer, Karen Fontijn, William Hutchison, Emmanuel Kazimoto, Kathy Whaler, Tim J. Wright
Summary: New observations of volcanic and magmatic activity in Africa are reshaping our understanding of continental rifting and highlighting the associated hazards. Despite efforts to shift from crisis response to reducing disaster risks, limited capacity in sub-Saharan Africa hinders effective mitigation of geohazards.
NATURE COMMUNICATIONS
(2021)
Article
Geosciences, Multidisciplinary
K. A. Whaler, M. D. Hammer, C. C. Finlay, N. Olsen
Summary: A geomagnetic jerk was observed in the Pacific region in 2017 using Swarm satellite data. The study used inversion of time series data to analyze the spatial and temporal characteristics of core surface flow. The results showed a significant change in azimuthal acceleration during the jerk epoch, with a near disappearance at 160 degrees W. Unlike previous studies, this research does not rely on symmetries, geostrophy, or filtering methods, and does not involve stochastic models or numerical simulations.
GEOPHYSICAL RESEARCH LETTERS
(2022)
Article
Geosciences, Multidisciplinary
Relly Margiono, Christopher W. Turbitt, Ciaran D. Beggan, Kathryn A. Whaler
Summary: Measurement of the geomagnetic field in Indonesia is conducted by the Meteorological, Climatological, and Geophysical Agency (BMKG). Some challenges include observatories not sharing data with the World Data Centre of Geomagnetism (WDC-G), low data quality due to noise, and limited training and knowledge in data processing. Efforts to improve data quality and recommendations for other institutes are discussed in the report. Definitive data from Indonesian observatories for the years 2010 to 2018 are now available in the WDC-G.
GEOSCIENTIFIC INSTRUMENTATION METHODS AND DATA SYSTEMS
(2021)
Article
Astronomy & Astrophysics
Ciaran D. Beggan, Gemma S. Richardson, Orsi Baillie, Juliane Hubert, Alan W. P. Thomson
Summary: Significant geoelectric fields can damage grounded infrastructure during intense geomagnetic activity. Understanding the effects of space weather on grounded infrastructure involves studying the spatial and temporal variation of the geoelectric field. Long-term monitoring at observatories in the UK allows comparisons with models and predictions for selected storm times, showing good correlation. Modeling approaches, including a thin-sheet model of Britain, provide estimates for historic storms that may underestimate the true value of peak geoelectric fields.
JOURNAL OF SPACE WEATHER AND SPACE CLIMATE
(2021)
Article
Geosciences, Multidisciplinary
Jo Ann Joselyn, Alik Ismail-Zadeh, Tom Beer, Harsh Gupta, Masaru Kono, Uri Shamir, Michael Sideris, Kathryn Whaler
HISTORY OF GEO- AND SPACE SCIENCES
(2019)