Article
Mathematics
Olga Sheremetyeva
Summary: The article investigates a large-scale model of an a?-dynamo in the low-mode approximation. The intensity of the a-effect is regulated by a process with hereditarity properties. The stability of the MHD-system solution is studied based on the control parameters and the parameters of the alternating kernel. The results are represented on the phase plane, and the change in pattern depending on the damping coefficient, damping frequency, and waiting time is compared with previous studies.
Article
Astronomy & Astrophysics
R. A. Kislov, H. V. Malova, O. V. Khabarova, L. M. Zelenyi, U. P. Antsiferova
Summary: Boundary current sheets (CSs) can form in collisionless space plasmas around exoplanets and cold stars. These CSs are curved surfaces carrying electric current, similar to planetary ionospheres, magnetopauses, or stellar coronas. At smaller scales, some CSs can be imagined as planar current layers of finite scale parallel to a celestial object's surface. The combination of gravitational and magnetic fields can influence the dynamics of charged particles in the CSs and alter the structure of both the current layer and magnetic field. This study presents a generalized model that considers a multi-ion plasma composition and a magnetic field configuration with shear. The results show that the structure of CSs becomes more complex due to the drift motion of plasma particles in the crossed gravitational and magnetic fields.
ASTROPHYSICAL JOURNAL
(2023)
Article
Astronomy & Astrophysics
Hongzhe Zhou, Eric G. Blackman
Summary: The study combines analytical approaches with simulations to investigate the shear-current effect in mean-field dynamo theory. The results show that the kinetic contribution can transition from positive to negative values with the kinetic energy spectral index, while the magnetic contribution remains negative regardless of the spectral index.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Neco Kriel, James R. Beattie, Amit Seta, Christoph Federrath
Summary: The turbulent dynamo mechanism involves converting turbulent kinetic energy into magnetic energy and determining the scales at which magnetic fields concentrate, with a focus on the roles of viscous and resistive scales. Through numerical simulations, the dependence of characteristic scales on kinematic phases is explored, showing a principal dependence on the resistive scale k(eta). The study reveals dichotomies in the dynamo properties based on different hydrodynamic Reynolds numbers, with a minimum critical value of Re-crit = 100 for turbulent dynamo action.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Physics, Multidisciplinary
Akash Biswas, Bidya Binay Karak, Robert Cameron
Summary: A striking feature of the solar cycle is the migration of sunspots from midlatitudes to the equator over time. The level of activity and width of sunspot belts increase rapidly and then decline, while in the late stages of the cycle, the statistical properties remain the same regardless of the cycle's strength during its rise and maximum phases.
PHYSICAL REVIEW LETTERS
(2022)
Article
Astronomy & Astrophysics
Amit Seta, Christoph Federrath
Summary: Magnetic fields in the turbulent interstellar medium play an important role in star-forming galaxies. This study investigates the properties of the turbulent dynamo in different phases, showing that the growth rate of magnetic fields is similar in both warm and cold phases. Additionally, it is found that the final ratio of magnetic to turbulent kinetic energy is lower in the cold phase.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(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
Alexander Mordvinov, Bidya Binay Karak, Dipankar Banerjee, Elena M. Golubeva, Anna Khlystova, Anastasiya Zhukova, Pawan Kumar
Summary: Detailed study of solar activity cycles reveals important conclusions about polar field reversals and the causal relationship between polar field formation and magnetic flux transport. The characteristics of different solar activity cycles are influenced by the spatiotemporal organization and properties of emergent magnetic flux, leading to complex restructuring of high-latitude magnetic fields.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2022)
Article
Astronomy & Astrophysics
Qirong Jiao, Jie Jiang, Zi-Fan Wang
Summary: This study investigates the tilt angles of sunspot groups in relation to the generation of the poloidal magnetic field in the Babcock-Leighton dynamo. The results show that the tilt coefficient is indeed anti-correlated with the cycle strength, with strong statistical significance. Different methods in handling uncertainties were found to be responsible for the controversial nature of previous results. Additionally, the study reveals a linear vs. square-root dependence of tilts on latitudes for weak vs. strong cycles.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Multidisciplinary Sciences
Archie F. A. Bott, Petros Tzeferacos, Laura Chen, Charlotte A. J. Palmer, Alexandra Rigby, Anthony R. Bell, Robert Bingham, Andrew Birkel, Carlo Graziani, Dustin H. Froula, Joseph Katz, Michel Koenig, Matthew W. Kunz, Chikang Li, Jena Meinecke, Francesco Miniati, Richard Petrasso, Hye-Sook Park, Bruce A. Remington, Brian Reville, J. Steven Ross, Dongsu Ryu, Dmitri Ryutov, Fredrick H. Seguin, Thomas G. White, Alexander A. Schekochihin, Donald Q. Lamb, Gianluca Gregori
Summary: Understanding magnetic field generation and amplification in turbulent plasma is crucial for explaining observations of magnetic fields in the universe. This study validates a theoretical framework for the origin and sustainment of these fields, and reports an experiment on laboratory plasma dynamo with Pm & 1. By characterizing plasma evolution and measuring various properties, it is shown that plasma turbulence from strong shear can generate fields more efficiently than previously thought, potentially explaining large-scale fields in astrophysical systems.
PROCEEDINGS OF THE NATIONAL ACADEMY OF SCIENCES OF THE UNITED STATES OF AMERICA
(2021)
Review
Astronomy & Astrophysics
Sonia M. Tikoo, Alexander J. Evans
Summary: This study explores the importance of magnetic fields in planetary evolution, revealing the magnetic and evolutionary histories of Mercury, Earth, Mars, the Moon, and several planetesimals through spacecraft-based studies and paleomagnetic research. The geometries, intensities, and longevities of dynamo fields can provide information on core processes and planetary thermal evolution.
ANNUAL REVIEW OF EARTH AND PLANETARY SCIENCES
(2022)
Article
Astronomy & Astrophysics
Naveen Jingade, Nishant K. Singh
Summary: In this study, we investigate the impact of temporal fluctuations in kinetic helicity on the generation of large-scale magnetic fields in the presence of a background linear shear flow. Our findings show that growing solutions can be obtained when the correlation time of helicity is greater than the correlation time of velocity. Interestingly, under certain conditions, the axisymmetric modes exhibit non-monotonic behavior in relation to shear rate.
MONTHLY NOTICES OF THE ROYAL ASTRONOMICAL SOCIETY
(2021)
Article
Astronomy & Astrophysics
Bhishek Manek, Nicholas Brummell
Summary: This paper investigates the formation and evolution mechanisms of solar active regions and sunspots, revealing a selection rule for the rise of tube-like flux concentrations and explaining the solar hemispheric helicity rule. Theoretical models and Monte Carlo simulations are utilized to predict and explain the observed scatter in the rule and its variation over the solar cycle in more detail.
ASTROPHYSICAL JOURNAL
(2021)
Article
Astronomy & Astrophysics
D. V. Boneva, E. A. Mikhailov, M. V. Pashentseva, D. D. Sokoloff
Summary: By proposing a model using similar approaches as in galactic disks, the study shows that the magnetic field of an accretion disk is strictly dependent on boundary conditions, with zero conditions and a fixed magnetic field at the inner boundary helping to avoid solutions greater than the equipartition field.
ASTRONOMY & ASTROPHYSICS
(2021)
Article
Physics, Multidisciplinary
Alisa K. Galishnikova, Matthew W. Kunz, Alexander A. Schekochihin
Summary: The study demonstrates that turbulence in conducting plasma can amplify seed magnetic fields, leading to the formation of folded structures which become unstable to tearing during the nonlinear stage of dynamo. This disruption of folds by tearing increases the ratio of viscous-to-resistive dissipation.
Article
Physics, Fluids & Plasmas
Mouloud Kessar, Franck Plunian, Rodion Stepanov, Guillaume Balarac
Article
Physics, Fluids & Plasmas
M. Kessar, G. Balarac, F. Plunian
PHYSICS OF PLASMAS
(2016)
Article
Mechanics
Rodion Stepanov, Franck Plunian
FLUID DYNAMICS RESEARCH
(2018)
Article
Geochemistry & Geophysics
Z. Tigrine, H. -C. Nataf, N. Schaeffer, P. Cardin, F. Plunian
GEOPHYSICAL JOURNAL INTERNATIONAL
(2019)
Article
Physics, Fluids & Plasmas
Shubhadeep Sadhukhan, Roshan Samue, Franck Plunian, Rodion Stepanov, Ravi Samtaney, Mahendra Kumar Varma
PHYSICAL REVIEW FLUIDS
(2019)
Article
Physics, Fluids & Plasmas
Franck Plunian, Rodion Stepanov, Mahendra Kumar Verma
JOURNAL OF PLASMA PHYSICS
(2019)
Article
Mechanics
Franck Plunian, Andrei Teimurazov, Rodion Stepanov, Mahendra Kumar Verma
JOURNAL OF FLUID MECHANICS
(2020)
Article
Physics, Fluids & Plasmas
Franck Plunian, Thierry Alboussiere
Summary: This study investigates the impact of anisotropic electrical conductivity conjugated to anisotropic magnetic permeability on dynamo action, revealing a competition between the two anisotropies and the impossibility of dynamo effect if they are identical. Furthermore, it is found that even with isotropic electrical conductivity, the dynamo effect can still occur as long as the magnetic permeability is anisotropic.
JOURNAL OF PLASMA PHYSICS
(2021)
Article
Mechanics
Franck Plunian, Thierry Alboussiere
Summary: In the limit of large magnetic Reynolds numbers, a smooth differential rotation can result in fast dynamo action if the electrical conductivity or magnetic permeability is anisotropic. In the case of infinite shear, such as between two rotating solid bodies, the anisotropic dynamo becomes furious, with the magnetic growth rate increasing towards infinity with an increasing magnetic Reynolds number.
JOURNAL OF FLUID MECHANICS
(2022)
Article
Multidisciplinary Sciences
T. Alboussiere, F. Plunian, M. Moulin
Summary: Measurements of dynamo action in the new experimental set-up named Fury, based on anisotropic electrical conductivity, are reported. The structure of the axisymmetric magnetic field produced is found to be close to the numerical modelling. The experimental dynamo behaves as expected for a kinematic dynamo, with a threshold velocity limit.
PROCEEDINGS OF THE ROYAL SOCIETY A-MATHEMATICAL PHYSICAL AND ENGINEERING SCIENCES
(2022)
Article
Physics, Fluids & Plasmas
T. Alboussiere, K. Drif, F. Plunian
Article
Physics, Multidisciplinary
Franck Plunian, Thierry Alboussiere
PHYSICAL REVIEW RESEARCH
(2020)
Article
Mechanics
Mahendra K. Verma, R. Stepanov, F. Plunian
MAGNETOHYDRODYNAMICS
(2019)
Proceedings Paper
Materials Science, Multidisciplinary
R. Stepanov, F. Plunian
WINTER SCHOOL ON CONTINUOUS MEDIA MECHANICS
(2017)
Proceedings Paper
Engineering, Electrical & Electronic
Rodion Stepanov, Andrei Teimurazov, Valerij Titov, Mahendra K. Verma, Satyajit Barman, Abhishek Kumar, Franck Plunian
2017 IVANNIKOV ISPRAS OPEN CONFERENCE (ISPRAS)
(2017)
