Special Issue "Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows"

A special issue of Atmosphere (ISSN 2073-4433). This special issue belongs to the section "Biosphere/Hydrosphere/Land–Atmosphere Interactions".

Deadline for manuscript submissions: 15 March 2020.

Special Issue Editor

Dr. Raffaele Marino
E-Mail Website
Guest Editor
Laboratoire de Mécanique des Fluides et d'Acoustique, CNRS, École Centrale de Lyon, Université de Lyon, Écully, France
Interests: fluid mechanics; plasma physics; geophysical and astrophysical flows

Special Issue Information

Dear Colleagues,

The aim of this Special Issue is to gather recent studies on turbulent dynamics and transport properties in fluid and plasma frameworks in the presence of stratification and/or rotation, as well as under the influence of external and self-generated magnetic fields. In these systems, density profiles, rotation axes, and magnetic fields establish preferential directions that break isotropy at some scales, allow for the propagation of waves, and may lead to the creation of helicity and the onset of dynamos. Turbulence thus has to compete with waves, and the interplay between these two energy transfer mechanisms plays a crucial role in determining the transport of momentum, particles, active/passive scalars within the flows, dissipation properties, and in promoting the exchange between kinetic and potential or magnetic energy. Stratified, rotating fluid and plasma flows are the reference physical frameworks of planetary atmospheres and interiors, of the Earth’s oceans, of the solar wind, the Sun, and also of those regions where the solar–terrestrial coupling is achieved (magnetosphere and ionosphere).

It is therefore possible to leverage an integrated approach that combines investigations using theoretical, numerical. and experimental modeling, with state-of-the-art space and ground-based observations of geophysical and astrophysical flows to advance knowledge of both fundamental phenomena in fluids and plasmas, as well as the complex dynamics of the Earth climate and the heliosphere systems. Research articles and short reviews focusing on the key subjects proposed here are all welcome and will serve the purpose of this Special Issue.

Dr. Raffaele Marino
Guest Editor

Manuscript Submission Information

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Keywords

  • Turbulence
  • Waves
  • Instabilities
  • Stratification
  • Rotation
  • Active and passive scalars
  • Particles
  • Dynamos
  • Helicity
  • Geophysical fluids
  • Space and fundamental plasmas

Published Papers (7 papers)

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Research

Open AccessArticle
Coupling Large Eddies and Waves in Turbulence: Case Study of Magnetic Helicity at the Ion Inertial Scale
Atmosphere 2020, 11(2), 203; https://doi.org/10.3390/atmos11020203 (registering DOI) - 14 Feb 2020
Abstract
In turbulence, for neutral or conducting fluids, a large ratio of scales is excited because of the possible occurrence of inverse cascades to large, global scales together with direct cascades to small, dissipative scales, as observed in the atmosphere and oceans, or in [...] Read more.
In turbulence, for neutral or conducting fluids, a large ratio of scales is excited because of the possible occurrence of inverse cascades to large, global scales together with direct cascades to small, dissipative scales, as observed in the atmosphere and oceans, or in the solar environment. In this context, using direct numerical simulations with forcing, we analyze scale dynamics in the presence of magnetic fields with a generalized Ohm’s law including a Hall current. The ion inertial length ϵ H serves as the control parameter at fixed Reynolds number. Both the magnetic and generalized helicity—invariants in the ideal case—grow linearly with time, as expected from classical arguments. The cross-correlation between the velocity and magnetic field grows as well, more so in relative terms for a stronger Hall current. We find that the helical growth rates vary exponentially with ϵ H , provided the ion inertial scale resides within the inverse cascade range. These exponential variations are recovered phenomenologically using simple scaling arguments. They are directly linked to the wavenumber power-law dependence of generalized and magnetic helicity, k - 2 , in their inverse ranges. This illustrates and confirms the important role of the interplay between large and small scales in the dynamics of turbulent flows. Full article
Open AccessArticle
GPU Parallelization of a Hybrid Pseudospectral Geophysical Turbulence Framework Using CUDA
Atmosphere 2020, 11(2), 178; https://doi.org/10.3390/atmos11020178 - 08 Feb 2020
Abstract
An existing hybrid MPI-OpenMP scheme is augmented with a CUDA-based fine grain parallelization approach for multidimensional distributed Fourier transforms, in a well-characterized pseudospectral fluid turbulence code. Basics of the hybrid scheme are reviewed, and heuristics provided to show a potential benefit of the [...] Read more.
An existing hybrid MPI-OpenMP scheme is augmented with a CUDA-based fine grain parallelization approach for multidimensional distributed Fourier transforms, in a well-characterized pseudospectral fluid turbulence code. Basics of the hybrid scheme are reviewed, and heuristics provided to show a potential benefit of the CUDA implementation. The method draws heavily on the CUDA runtime library to handle memory management and on the cuFFT library for computing local FFTs. The manner in which the interfaces to these libraries are constructed, and ISO bindings utilized to facilitate platform portability, are discussed. CUDA streams are implemented to overlap data transfer with cuFFT computation. Testing with a baseline solver demonstrated significant aggregate speed-up over the hybrid MPI-OpenMP solver by offloading to GPUs on an NVLink-based test system. While the batch streamed approach provided little benefit with NVLink, we saw a performance gain of 30 % when tuned for the optimal number of streams on a PCIe-based system. It was found that strong GPU scaling is nearly ideal, in all cases. Profiling of the CUDA kernels shows that the transform computation achieves 15% of the attainable peak FlOp-rate based on a roofline model for the system. In addition to speed-up measurements for the fiducial solver, we also considered several other solvers with different numbers of transform operations and found that aggregate speed-ups are nearly constant for all solvers. Full article
Open AccessArticle
Nonlinear Effects on the Precessional Instability in Magnetized Turbulence
Atmosphere 2020, 11(1), 14; https://doi.org/10.3390/atmos11010014 - 22 Dec 2019
Abstract
By means of direct numerical simulations (DNS), we study the impact of an imposed uniform magnetic field on precessing magnetohydrodynamic homogeneous turbulence with a unit magnetic Prandtl number. The base flow which can trigger the precessional instability consists of the superposition of a [...] Read more.
By means of direct numerical simulations (DNS), we study the impact of an imposed uniform magnetic field on precessing magnetohydrodynamic homogeneous turbulence with a unit magnetic Prandtl number. The base flow which can trigger the precessional instability consists of the superposition of a solid-body rotation around the vertical ( x 3 ) axis (with rate Ω ) and a plane shear (with rate S = 2 ε Ω ) viewed in a frame rotating (with rate Ω p = ε Ω ) about an axis normal to the plane of shear and to the solid-body rotation axis and under an imposed magnetic field that aligns with the solid-body rotation axis ( B Ω ) . While rotation rate and Poincaré number are fixed, Ω = 20 and ε = 0.17 , the B intensity was varied, B = 0.1 , 0.5 , and 2.5 , so that the Elsasser number is about Λ = 0.1 , 2.5 and 62.5 , respectively. At the final computational dimensionless time, S t = 2 ε Ω t = 67 , the Rossby number Ro is about 0.1 characterizing rapidly rotating flow. It is shown that the total (kinetic + magnetic) energy ( E ) , production rate ( P ) due the basic flow and dissipation rate ( D ) occur in two main phases associated with different flow topologies: (i) an exponential growth and (ii) nonlinear saturation during which these global quantities remain almost time independent with P D . The impact of a "strong" imposed magnetic field ( B = 2.5 ) on large scale structures at the saturation stage is reflected by the formation of structures that look like filaments and there is no dominance of horizontal motion over the vertical (along the solid-rotation axis) one. The comparison between the spectra of kinetic energy E ( κ ) ( k ) , E ( κ ) ( k , k = 1 , 2 ) and E κ ) ( k , k = 0 ) at the saturation stage reveals that, at large horizontal scales, the major contribution to E ( κ ) ( k ) does not come only from the mode k = 0 but also from the k = 1 mode which is the most energetic. Only at very large horizontal scales at which E ( κ ) ( k ) E 2 D ( κ ) ( k ) , the flow is almost two-dimensional. In the wavenumbers range 10 k 40 , the spectra E ( κ ) ( k ) and E ( κ ) ( k , k = 0 ) respectively follow the scaling k 2 and k 3 . Unlike the velocity field the magnetic field remains strongly three-dimensional for all scales since E 2 D ( m ) ( k ) E ( m ) ( k ) . At the saturation stage, the Alfvén ratio between kinetic and magnetic energies behaves like k 2 for B k / ( 2 ε Ω ) < 1 . Full article
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Open AccessArticle
Study of Galactic Cosmic-Ray Flux Modulation by Interplanetary Plasma Structures for the Evaluation of Space Instrument Performance and Space Weather Science Investigations
Atmosphere 2019, 10(12), 749; https://doi.org/10.3390/atmos10120749 - 28 Nov 2019
Cited by 1
Abstract
The role of high-energy particles in limiting the performance of on-board instruments was studied for the European Space Agency (ESA) Laser Interferometer Space Antenna (LISA) Pathfinder (LPF) and ESA/National Astronautics and Space Administration Solar Orbiter missions. Particle detectors (PD) placed on board the [...] Read more.
The role of high-energy particles in limiting the performance of on-board instruments was studied for the European Space Agency (ESA) Laser Interferometer Space Antenna (LISA) Pathfinder (LPF) and ESA/National Astronautics and Space Administration Solar Orbiter missions. Particle detectors (PD) placed on board the LPF spacecraft allowed for testing the reliability of pre-launch predictions of galactic cosmic-ray (GCR) energy spectra and for studying the modulation of proton and helium overall flux above 70 MeV n 1 on a day-by-day basis. GCR flux variations up to approximately 15% in less than a month were observed with LPF orbiting around the Lagrange point L1 between 2016 and 2017. These variations appeared barely detected or undetected in neutron monitors. In this work the LPF data and contemporaneous observations carried out with the magnetic spectrometer AMS-02 experiment are considered to show the effects of GCR flux short-term variations with respect to monthly averaged measurements. Moreover, it is shown that subsequent large-scale interplanetary structures cause a continuous modulation of GCR fluxes. As a result, small Forbush decreases cannot be considered good proxies for the transit of interplanetary coronal mass ejections and for geomagnetic storm forecasting. Full article
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Open AccessArticle
Scaling Properties of Atmospheric Wind Speed in Mesoscale Range
Atmosphere 2019, 10(10), 611; https://doi.org/10.3390/atmos10100611 - 10 Oct 2019
Abstract
The scaling properties of turbulent flows are well established in the inertial sub-range. However, those of the synoptic-scale motions are less known, also because of the difficult analysis of data presenting nonstationary and periodic features. Extensive analysis of experimental wind speed data, collected [...] Read more.
The scaling properties of turbulent flows are well established in the inertial sub-range. However, those of the synoptic-scale motions are less known, also because of the difficult analysis of data presenting nonstationary and periodic features. Extensive analysis of experimental wind speed data, collected at the Mauna Loa Observatory of Hawaii, is performed using different methods. Empirical Mode Decomposition, interoccurrence times statistics, and arbitrary-order Hilbert spectral analysis allow to eliminate effects of large-scale modulations, and provide scaling properties of the field fluctuations (Hurst exponent, interoccurrence distribution, and intermittency correction). The obtained results suggest that the mesoscale wind dynamics owns features which are typical of the inertial sub-range turbulence, thus extending the validity of the turbulent cascade phenomenology to scales larger than observed before. Full article
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Open AccessArticle
Evolution of Turbulence in the Kelvin–Helmholtz Instability in the Terrestrial Magnetopause
Atmosphere 2019, 10(9), 561; https://doi.org/10.3390/atmos10090561 - 18 Sep 2019
Cited by 1
Abstract
The dynamics occurring at the terrestrial magnetopause are investigated by using Geotail and THEMIS spacecraft data of magnetopause crossings during ongoing Kelvin–Helmholtz instability. Properties of plasma turbulence and intermittency are presented, with the aim of understanding the evolution of the turbulence as a [...] Read more.
The dynamics occurring at the terrestrial magnetopause are investigated by using Geotail and THEMIS spacecraft data of magnetopause crossings during ongoing Kelvin–Helmholtz instability. Properties of plasma turbulence and intermittency are presented, with the aim of understanding the evolution of the turbulence as a result of the development of Kelvin–Helmholtz instability. The data have been tested against standard diagnostics for intermittent turbulence, such as the autocorrelation function, the spectral analysis and the scale-dependent statistics of the magnetic field increments. A quasi-periodic modulation of different scaling exponents may exist along the direction of propagation of the Kelvin–Helmholtz waves along the Geocentric Solar Magnetosphere coordinate system (GSM), and it is visible as a quasi-periodic modulation of the scaling exponents we have studied. The wave period associated with such oscillation was estimated to be approximately 6.4 Earth Radii ( R E ). Furthermore, the amplitude of such modulation seems to decrease as the measurements are taken further away from the Earth along the magnetopause, in particular after X ( G S M ) 15 R E . The observed modulation seems to persist for most of the parameters considered in this analysis. This suggests that a kind of signature related to the development of the Kelvin–Helmholtz instabilities could be present in the statistical properties of the magnetic turbulence. Full article
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Open AccessArticle
Evidence for Rayleigh-Taylor Plasma Instability at the Front of Solar Coronal Mass Ejections
Atmosphere 2019, 10(8), 468; https://doi.org/10.3390/atmos10080468 - 15 Aug 2019
Abstract
This work focuses on the interaction of a Coronal Mass Ejection (CME) with the ambient solar corona, by studying the spatial and temporal evolution of the density fluctuations observed by the SOHO/UV Coronagraph Spectrometer (UVCS) during the CME. The investigation is performed by [...] Read more.
This work focuses on the interaction of a Coronal Mass Ejection (CME) with the ambient solar corona, by studying the spatial and temporal evolution of the density fluctuations observed by the SOHO/UV Coronagraph Spectrometer (UVCS) during the CME. The investigation is performed by applying a wavelet analysis to the HI Ly α 1216 Å line intensity fluctuations observed with UVCS during the CME occurred on 24 December 2006. Strong and coherent fluctuations, with a significant spatial periodicity of about 84 Mm 0.12 R , are shown to develop in about an hour along the front of the CME. The results seem to indicate the Rayleigh-Taylor (RT) instability, susceptible to the deceleration of the heavier fluid of the CME front into the lighter surrounding coronal plasma, as the likely mechanism underlying the generation of the observed plasma fluctuations. This could be the first inference of the RT instability in the outer solar corona in UV, due to the transit of a CME front in the quiet coronal plasma; this interpretation is also supported by a linear magnetohydrodynamic analysis of the RT instability. Full article
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