Submit to Atmosphere Review for Atmosphere Propose a Special Issue

Journal Menu

Journal Browser

Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows

Print Special Issue Flyer
Special Issue Editors
Special Issue Information
Keywords
Published Papers

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

Deadline for manuscript submissions: closed (15 August 2020) | Viewed by 41406

Share This Special Issue

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, 69134 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

Manuscripts should be submitted online at www.mdpi.com by registering and logging in to this website. Once you are registered, click here to go to the submission form. Manuscripts can be submitted until the deadline. All submissions that pass pre-check are peer-reviewed. Accepted papers will be published continuously in the journal (as soon as accepted) and will be listed together on the special issue website. Research articles, review articles as well as short communications are invited. For planned papers, a title and short abstract (about 100 words) can be sent to the Editorial Office for announcement on this website.

Submitted manuscripts should not have been published previously, nor be under consideration for publication elsewhere (except conference proceedings papers). All manuscripts are thoroughly refereed through a single-blind peer-review process. A guide for authors and other relevant information for submission of manuscripts is available on the Instructions for Authors page. Atmosphere is an international peer-reviewed open access monthly journal published by MDPI.

Please visit the Instructions for Authors page before submitting a manuscript. The Article Processing Charge (APC) for publication in this open access journal is 2400 CHF (Swiss Francs). Submitted papers should be well formatted and use good English. Authors may use MDPI's English editing service prior to publication or during author revisions.

Keywords

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

Published Papers (15 papers)

Download All Papers

Research

9 pages, 325 KiB

Open AccessArticle

Persistence of Ion Cyclotron Waves and Stochasticity of Kinetic Alfvén Waves in the Solar Wind

by Daniele Telloni

Atmosphere 2021, 12(1), 44; https://doi.org/10.3390/atmos12010044 - 30 Dec 2020

Cited by 3 | Viewed by 1487

Abstract

This paper investigates the nature of the physical processes underlying the origin of the Ion Cyclotron Waves (ICWs) and Kinetic Alfvén Waves (KAWs) in the solar wind, by studying their Waiting Time Distributions (WTDs). The results show that ICWs and KAWs do not share common statistical properties: while KAWs independently occur as stochastic, uncorrelated wave packets governed by Poisson statistics, ICWs are highly correlated, thus departing from the Poisson hypothesis. The results based on the WTD analysis may cast more light on the mechanisms actively at work in the generation of the two wave modes. Specifically, while the stochastic character of KAWs may be reminiscent of the random convection-driven jostling of the flux-tube foot-points that generates the Alfvén waves in the lower solar atmosphere, the correlations among the ICW events can be effectively explained on the basis of the persistent nature of the mechanism underlying the local origin of ICWs, namely the proton cyclotron instability. Alternative explanations for the observed distribution of ICW waiting times, based on a piecewise-constant Poisson process involving time-varying rates, are also reported. Full article

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

31 pages, 4002 KiB

Open AccessArticle

Generalized Description of Intermittency in Turbulence via Stochastic Methods

by Jan Friedrich and Rainer Grauer

Atmosphere 2020, 11(9), 1003; https://doi.org/10.3390/atmos11091003 - 19 Sep 2020

Cited by 5 | Viewed by 2384

Abstract

We present a generalized picture of intermittency in turbulence that is based on the theory of stochastic processes. To this end, we rely on the experimentally and numerically verified finding by R. Friedrich and J. Peinke [Phys. Rev. Lett. 78, 863 (1997)] that allows for an interpretation of the turbulent energy cascade as a Markov process of velocity increments in scale. It is explicitly shown that phenomenological models of turbulence, which are characterized by scaling exponents

ζ_{n}

of velocity increment structure functions, can be reproduced by the Kramers–Moyal expansion of the velocity increment probability density function that is associated with a Markov process. We compare the different sets of Kramers–Moyal coefficients of each phenomenology and deduce that an accurate description of intermittency should take into account an infinite number of coefficients. This is demonstrated in more detail for the case of Burgers turbulence that exhibits pronounced intermittency effects. Moreover, the influence of nonlocality on Kramers–Moyal coefficients is investigated by direct numerical simulations of a generalized Burgers equation. Depending on the balance between nonlinearity and nonlocality, we encounter different intermittency behavior that ranges from self-similarity (purely nonlocal case) to intermittent behavior (intermediate case that agrees with Yakhot’s mean field theory [Phys. Rev. E 63 026307 (2001)]) to shock-like behavior (purely nonlinear Burgers case). Full article

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

18 pages, 2945 KiB

Open AccessArticle

Fast Camera Analysis of Plasma Instabilities in Hall Effect Thrusters Using a POD Method under Different Operating Regimes

by Victor Désangles, Sergey Shcherbanev, Thomas Charoy, Noé Clément, Clarence Deltel, Pablo Richard, Simon Vincent, Pascal Chabert and Anne Bourdon

Atmosphere 2020, 11(5), 518; https://doi.org/10.3390/atmos11050518 - 18 May 2020

Cited by 10 | Viewed by 3213

Abstract

Even after half a century of development, many phenomena in Hall Effect Thrusters are still not well-understood. While numerical studies are now widely used to study this highly non-linear system, experimental diagnostics are needed to validate their results and identify specific oscillations. By varying the cathode heating current, its emissivity is efficiently controlled and a transition between two functioning regimes of a low power thruster is observed. This transition implies a modification of the axial electric field and of the plasma plume shape. High-speed camera imaging is performed and the data are analysed using a Proper Orthogonal Decomposition method to isolate the different types of plasma fluctuations occurring simultaneously. The low-frequency breathing mode is observed, along with higher frequency rotating modes that can be associated to rotating spokes or gradient-induced instabilities. These rotating modes are observed while propagating outside the thruster channel. The reduction of the cathode emissivity beyond the transition comes along with a disappearance of the breathing mode, which could improve the thruster performance and stability. Full article

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

12 pages, 1737 KiB

Open AccessArticle

Scale-Dependent Turbulent Dynamics and Phase-Space Behavior of the Stable Atmospheric Boundary Layer

by Francesco Carbone, Tommaso Alberti, Luca Sorriso-Valvo, Daniele Telloni, Francesca Sprovieri and Nicola Pirrone

Atmosphere 2020, 11(4), 428; https://doi.org/10.3390/atmos11040428 - 23 Apr 2020

Cited by 4 | Viewed by 2563

Abstract

The structure of turbulent dynamics in a stable atmospheric boundary layer was studied by means of a phase-space description. Data from the CASES-99 experiment, decomposed in local modes (with increasing time scale) using empirical mode decomposition, were analyzed in order to extract the proper time lag and the embedding dimension of the phase-space manifold, and subsequently to estimate their scale-dependent correlation dimension. Results show that the dynamics are low-dimensional and anisotropic for a large scale, where the flow is dominated by the bulk motion. Then, they become progressively more high-dimensional while transiting into the inertial sub-range. Finally, they reach three-dimensionality in the range of scales compatible with the center of the inertial sub-range, where the phase-space-filling turbulent fluctuations dominate the dynamics. Full article

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

29 pages, 7165 KiB

Open AccessArticle

Partitioning Waves and Eddies in Stably Stratified Turbulence

by Henri Lam, Alexandre Delache and Fabien S Godeferd

Atmosphere 2020, 11(4), 420; https://doi.org/10.3390/atmos11040420 - 22 Apr 2020

Cited by 6 | Viewed by 3303

Abstract

We consider the separation of motion related to internal gravity waves and eddy dynamics in stably stratified flows obtained by direct numerical simulations. The waves’ dispersion relation links their angle of propagation to the vertical

θ

, to their frequency

ω

, so [...] Read more.

θ

, to their frequency

ω

, so that two methods are used for characterizing wave-related motion: (a) the concentration of kinetic energy density in the

(θ, ω)

map along the dispersion relation curve; and (b) a direct computation of two-point two-time velocity correlations via a four-dimensional Fourier transform, permitting to extract wave-related space-time coherence. The second method is more computationally demanding than the first. In canonical flows with linear kinematics produced by space-localized harmonic forcing, we observe the pattern of the waves in physical space and the corresponding concentration curve of energy in the

(θ, ω)

plane. We show from a simple laminar flow that the curve characterizing the presence of waves is distorted differently in the presence of a background convective mean velocity, either uniform or varying in space, and also when the forcing source is moving. By generalizing the observation from laminar flow to turbulent flow, this permits categorizing the energy concentration pattern of the waves in complex flows, thus enabling the identification of wave-related motion in a general turbulent flow with stable stratification. The advanced method (b) is finally used to compute the wave-eddy partition in the velocity–buoyancy fields of direct numerical simulations of stably stratified turbulence. In particular, we use this splitting in statistics as varied as horizontal and vertical kinetic energy, as well as two-point velocity and buoyancy spectra. Full article

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

18 pages, 3730 KiB

Open AccessArticle

Turbulence in a Coronal Loop Excited by Photospheric Motions

by Giuseppina Nigro, Francesco Malara, Antonio Vecchio, Leonardo Primavera, Francesca Di Mare, Vincenzo Carbone and Pierluigi Veltri

Atmosphere 2020, 11(4), 409; https://doi.org/10.3390/atmos11040409 - 20 Apr 2020

Cited by 1 | Viewed by 2458

Abstract

Photospheric motions are believed to be the source of coronal heating and of velocity fluctuations detected in the solar corona. A numerical model, based on the shell technique applied on reduced magnetohydrodynamics equations, is used to represent energy injection due to footpoint motions, storage and dissipation of energy in a coronal loop. Motions at the loop bases are simulated by random signals whose frequency-wavenumber spectrum reproduces features of photospheric motions: the p-mode peak and the low-frequency continuum. Results indicate that a turbulent state develops, dominated by magnetic energy, where dissipation takes place in an intermittent fashion. The nonlinear cascade is mainly controlled by velocity fluctuations, where resonant modes are dominant at high frequencies. Low frequency fluctuations present a power-law spectra and a bump at p-mode frequency; similar features are observed in velocity spectra detected in the corona. For typical loop parameters the energy input flux is comparable with that necessary to heat the quiet-Sun corona. Full article

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

15 pages, 313 KiB

Open AccessArticle

Probability Density Functions in Homogeneous and Isotropic Magneto-Hydrodynamic Turbulence

by Jan Friedrich

Atmosphere 2020, 11(4), 382; https://doi.org/10.3390/atmos11040382 - 14 Apr 2020

Cited by 5 | Viewed by 1778

Abstract

We derive a hierarchy of evolution equations for multi-point probability density functions in magneto-hydrodynamic (MHD) turbulence. We discuss the relation to the moment hierarchy in MHD turbulence formulated by Chandrasekhar (S. Chandrasekhar, Proc. R. Soc. Lond. A 1951, 204, 435–449) and derive a functional equation for a joint characteristic functional, which can be considered as the analogon to the Hopf functional in hydrodynamic turbulence. Furthermore, we develop a closure method for the evolution equation of the single-point magnetic field probability density function, which is based on a joint Gaussian assumption for unclosed terms. It is explicitly shown that this closure, together with the assumptions of homogeneity and isotropy, leads to vanishing nonlinear terms. We discuss the implications of this finding for magnetic field generation and give a brief outlook on an axisymmetric theory, which includes a mean magnetic field. Full article

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

16 pages, 1310 KiB

Open AccessArticle

Shallow Water Magnetohydrodynamics in Plasma Astrophysics. Waves, Turbulence, and Zonal Flows

by Arakel Petrosyan, Dmitry Klimachkov, Maria Fedotova and Timofey Zinyakov

Atmosphere 2020, 11(4), 314; https://doi.org/10.3390/atmos11040314 - 25 Mar 2020

Cited by 10 | Viewed by 3099

Abstract

The purpose of plasma astrophysics is the study and description of the flow of rotating plasma in order to understand the evolution of various objects in the universe, from stars and planetary systems to galaxies and galaxy clusters. A number of new applications and observations have appeared in recent years and actualized the problem of studying large-scale magnetohydrodynamic flows, such as a thin layer under the convective zone of the sun (solar tachocline), propagation of accreting matter in neutron stars, accretion disks in astrophysics, dynamics of neutron star atmospheres, and magnetoactive atmospheres of exoplanets tidally locked with their host star. The article aims to discuss a fundamental problem in the description and study of multiscale astrophysical plasma flows by studying its general properties characterizing different objects in the universe. We are dealing with the development of geophysical hydrodynamic ideas concerning substantial differences in plasma flow behavior due to the presence of magnetic fields and stratification. We discuss shallow water magnetohydrodynamic equations (one-layer and two-layer models) and two-dimensional magnetohydrodynamic equations as a basis for studying large-scale flows in plasma astrophysics. We discuss the novel set of equations in the external magnetic field. The following topics will be addressed: Linear theory of magneto-Rossby waves, three-wave interactions and related parametric instabilities, zonal flows, and turbulence. Full article

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

23 pages, 2535 KiB

Open AccessArticle

Coupling Large Eddies and Waves in Turbulence: Case Study of Magnetic Helicity at the Ion Inertial Scale

by Annick Pouquet, Julia E. Stawarz and Duane Rosenberg

Atmosphere 2020, 11(2), 203; https://doi.org/10.3390/atmos11020203 - 14 Feb 2020

Cited by 7 | Viewed by 2726

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 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,

\sim 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

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

22 pages, 638 KiB

Open AccessArticle

GPU Parallelization of a Hybrid Pseudospectral Geophysical Turbulence Framework Using CUDA

by Duane Rosenberg, Pablo D. Mininni, Raghu Reddy and Annick Pouquet

Atmosphere 2020, 11(2), 178; https://doi.org/10.3390/atmos11020178 - 08 Feb 2020

Cited by 24 | Viewed by 3155

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 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

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

24 pages, 1009 KiB

Open AccessArticle

Nonlinear Effects on the Precessional Instability in Magnetized Turbulence

by Abdelaziz Salhi, Amor Khlifi and Claude Cambon

Atmosphere 2020, 11(1), 14; https://doi.org/10.3390/atmos11010014 - 22 Dec 2019

Cited by 4 | Viewed by 2040

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.

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 \sim 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_{⊥}) \sim E_{2 D}^{(κ)} (k_{⊥}),

the flow is almost two-dimensional. In the wavenumbers range

10 \leq k_{⊥} \leq 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

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

14 pages, 471 KiB

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

by Catia Grimani, Daniele Telloni, Simone Benella, Andrea Cesarini, Michele Fabi and Mattia Villani

Atmosphere 2019, 10(12), 749; https://doi.org/10.3390/atmos10120749 - 28 Nov 2019

Cited by 7 | Viewed by 3323

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 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

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

19 pages, 2265 KiB

Open AccessArticle

Scaling Properties of Atmospheric Wind Speed in Mesoscale Range

by Francesco Carbone, Daniele Telloni, Antonio G. Bruno, Ian M. Hedgecock, Francesco De Simone, Francesca Sprovieri, Luca Sorriso-Valvo and Nicola Pirrone

Atmosphere 2019, 10(10), 611; https://doi.org/10.3390/atmos10100611 - 10 Oct 2019

Cited by 7 | Viewed by 3222

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 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

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

17 pages, 694 KiB

Open AccessArticle

Evolution of Turbulence in the Kelvin–Helmholtz Instability in the Terrestrial Magnetopause

by Francesca Di Mare, Luca Sorriso-Valvo, Alessandro Retinò, Francesco Malara and Hiroshi Hasegawa

Atmosphere 2019, 10(9), 561; https://doi.org/10.3390/atmos10090561 - 18 Sep 2019

Cited by 9 | Viewed by 2935

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 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

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

19 pages, 11825 KiB

Open AccessArticle

Evidence for Rayleigh-Taylor Plasma Instability at the Front of Solar Coronal Mass Ejections

by Daniele Telloni, Francesco Carbone, Alessandro Bemporad and Ester Antonucci

Atmosphere 2019, 10(8), 468; https://doi.org/10.3390/atmos10080468 - 15 Aug 2019

Cited by 2 | Viewed by 2868

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.

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

_{⊙}

, 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

(This article belongs to the Special Issue Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows)

► Show Figures

Figure 1

Journal Menu

Journal Browser

Turbulence, Waves and Transport in Stratified, Rotating Fluid and Plasma Flows

Share This Special Issue

Special Issue Editor

Special Issue Information

Keywords

Published Papers (15 papers)

Research

Further Information

Guidelines

MDPI Initiatives

Follow MDPI