Zonal Structures Research Articles

Unexpected Regional Zonal Structures in Low Latitude Ionosphere Call for a High Longitudinal Resolution of the Global Ionospheric Maps

This study reports unexpected strong longitudinal structures from Global Navigation Satellite System (GNSS) derived total electron content (TEC) observations in the low-latitude ionosphere over Asia. The observations during 2019–2020 show diverse patterns in the zonal difference of regional TEC, even under geomagnetically quiet conditions. The TEC in the northern hemisphere occasionally exhibits drastic zonal gradients. The intense regional gradients in TEC span a longitudinal extent of about 20°. The higher values may appear on the east or the west side. Strong zonal gradients may appear in all seasons, regardless of geomagnetically quiet or active conditions. The 15 December 2019 and 16 March 2020 cases depict an intense zonal differences cluster in the narrow latitudinal band of 16°N to 28°N, spanning a regional scale smaller than the normal longitudinal structures. In contrast, the Global Ionospheric Maps (GIMs) with a longitudinal resolution of 5° show a much flatter zonal picture. Such intense and regional-scale zonal structures in the low-latitude ionosphere call for a high zonal resolution of GIMs in terms of better geographically distributed observations. Notably, no counterpart regional structures are found at the conjugated points in the southern hemisphere during the two cases. Although the physical drivers are not certain, the appearance only in the northern hemisphere possibly excludes the dominant contribution to forming the regional structures from the equatorial electric field.

Comparison of Radial and Zonal DC Distribution System for Hybrid-Powered Trimaran Vessels Power Flow Analysis

Two types of power grid structures have been applied to the shipboard, namely the radial and the zonal networks. These two distribution systems have different power characteristics transmitted to the bus panel. The power characteristics affect the power density of each bus at each level. This paper explores the power characteristics of the radial type and the zonal type power grid structures in a DC distribution system. The power flow of both distribution system types has been determined by the Adaptive Newton-Raphson method and simulated based on ship operation conditions using Electrical Power System Analysis Software (ETAP). In determining the power flow for the DC distribution system, one-line diagram modelling is developed in radial type and zonal type. The simulation parameters are adjusted to the operating conditions of the ship, namely sailing, manoeuvring, loading-unloading, and at the port. After that, a power flow simulation has been carried out using ETAP and has showed what had successfully implemented the power flow in the DC distribution system for radial and zonal types. The capacity of Power generation is adequate all through a ship operation. The characteristics of the transmitted power show that the zonal type has a higher efficiency rate than the radial type. The zonal type has a backup bus so that the electrical system's reliability is higher than the radial type. However, the power distributed to the equipment bus from the load bus, both the radial type and the zone type, has the exact power requirements.

Overview of the TJ-II stellarator research programme towards model validation in fusion plasmas

TJ-II stellarator results on modelling and validation of plasma flow asymmetries due to on-surface potential variations, plasma fuelling physics, Alfvén eigenmodes (AEs) control and stability, the interplay between turbulence and neoclassical (NC) mechanisms and liquid metals are reported. Regarding the validation of the neoclassically predicted potential asymmetries, its impact on the radial electric field along the flux surface has been successfully validated against Doppler reflectometry measurements. Research on the physics and modelling of plasma core fuelling with pellets and tracer encapsulated solid pellet injection has shown that, although post-injection particle radial redistributions can be understood qualitatively from NC mechanisms, turbulence and fluctuations are strongly affected during the ablation process. Advanced analysis tools based on transfer entropy have shown that radial electric fields do not only affect the radial turbulence correlation length but are also capable of reducing the propagation of turbulence from the edge into the scrape-off layer. Direct experimental observation of long range correlated structures show that zonal flow structures are ubiquitous in the whole plasma cross-section in the TJ-II stellarator. Alfvénic activity control strategies using ECRH and ECCD as well as the relation between zonal structures and AEs are reported. Finally, the behaviour of liquid metals exposed to hot and cold plasmas in a capillary porous system container was investigated.

Botanical-geographical differentiation and succession systems on the territory of the Republic of Bashkortostan

On the territory of the Republic of Bashkortostan the main regularities of landscape differentiation are manifested latitudinal zoning, altitudinal zoning and the barrier effect, which determine the territorial differentiation of the vegetation cover. The existing schemes of botanical-geographical and geobotanical zoning reflect these patterns. The largest zoning units are zonal structures (forest, forest-steppe and steppe regions), within which, on the basis of geological and geomorphological features, smaller taxonomic units are distinguished provinces, areas, districts. The zoning method proposed by S.M. Razumovsky which is based on the concept of a succession system is of interest. According to this concept, the vegetation cover of the Earth is divided between succession systems. The boundaries of successional systems are outlined by the boundaries of the geographical areas of key species edificators of indigenous forest phytocenoses. S.M. Razumovsky presented a scheme of botanical-geographical zoning, made on a small scale. The boundaries of succession systems, with the exception of some areas, are not delineated. The author set a goal: to determine a list of succession systems common on the territory of the Republic of Bashkortostan, to outline their boundaries and give their brief characteristics. As a result of literary sources study and analysis, the author has come to the conclusion that 4 succession systems are widespread on the territory of the Republic of Bashkortostan: 1) broad-leaved-dark coniferous forests with climax species of Siberian spruce, Siberian fir, pedunculate oak, heart-leaved linden and Norway maple; 2) dark coniferous forests, with climax species of Siberian spruce and Siberian fir; 3) broad-leaved forests with climax species of pedunculate oak, heart-leaved linden and Norway maple; 4) light coniferous forests with sub-climax species of Scots pine and Sukachev larch.

The zonal gradient structures of wintertime SST anomalies in the equatorial Pacific and their connection to the Walker circulation

The zonal gradient structures of wintertime SST anomalies in the equatorial Pacific and their connection to the Walker circulation

Gyrokinetic investigation of the nonlinear interaction of Alfvén instabilities and energetic particle-driven geodesic acoustic modes

This paper presents a study of the interaction between Alfvén modes and zonal structures, considering a realistic ASDEX Upgrade equilibrium. The results of gyrokinetic simulations with the global, electromagnetic, particle-in-cell code ORB5 are presented, where the modes are driven unstable by energetic particles with a bump-on-tail equilibrium distribution function, with radial density gradient. Two regimes have been observed. At low energetic particle concentration, the zonal structure (identified as an energetic particle-driven geodesic acoustic mode) is more unstable than the Alfvén mode. In the regime at high energetic particle concentration, the Alfvén mode is more unstable than the zonal structure. The interplay between the modes leads to a modification of their growth rates as well as to a modification of their saturation levels. The theoretical explanation of the mode interaction is given in terms of three-wave coupling of the energetic particle-driven geodesic acoustic mode and Alfvén mode, mediated by the curvature–pressure coupling term of the energetic particles.

Study on microstructure and properties of Mg/steel laser welding-brazing joint assisted by alternating magnetic field with Ni interlayer

The laser welding-brazing technology assisted by alternating magnetic field was adapted to Mg/steel dissimilar materials with Ni interlayer. Microstructure and mechanical properties of joints were compared with and without alternating magnetic field. The results showed that the weld width L was enlarged and ensured good weld formation and weld quality by applying the alternating magnetic field. The joint was comprised of Mg side weld zone, intermetallic compound (IMC) layer and steel side weld zone. The effect of mechanical occlusion was enhanced by the appearce of zonal structures of Fe–Ni solid solution in the Mg side weld zone and the serrated Mg2Ni in the brazing zone of IMC layer. A continuous nano scale AlNi layer formed in the fusion welding zone of IMC layer, which is conducive to strengthen the joint. The optimal joint assisted by appropriate alternating magnetic field was obtained with tensile and shear strength enhanced by nearly 15%.

The biomes of Western Australia: a vegetation-based approach using the zonality/ azonality conceptual framework

ABSTRACT Vegetation patterns of are the result of environmental drivers operating across a range of ecological and evolutionary scale. Those vegetation patterns at global and continental scales underpin the existence of large-scale functional entities called biomes. Traditionally, terrestrial biomes are recognised and distinguished by way of physiognomic traits thought to reflect the action of selective filters such as climate or disturbance (fire, grazing). This approach is well suited to recognising zonal biomes; it fails, however, to account for the role of other drivers such as soil and hydrology, potentially leading to over simplified representations of the biome patterns in ecologically complex regions such as Western Australia. It is, therefore, of vital importance to consider these patterns and processes and recognise the azonal biomes as well. Using a previously published physiognomic map of the vegetation of Western Australia, we adopted a bottom-up approach to translate the vegetation classification categories into a new biome classification of Western Australia that would more accurately account for the zonal and azonal structures recorded across the landscape. Five continental zonal biomes (Australian Eucalyptus Savanna, Australian Hummock Grassland, Mulga Shrubland, Australian Temperate Woodland, Australian Oceanic Temperate Forest) and one relict biome (Australian Vine Thicket) were identified. We further distinguished 34 types of azonal biomes, including three new ones: argillobiome, duplo-pedobiome and metallobiome. Predictive modelling (using Classification and Regression Trees) was used to define the potential extent of zonal biomes, with the model returning an overall accuracy of 90%. This study shows that a bottom-up approach based on vegetation maps can be used as an effective approximation for defining a robust classification of biome patterns. The predicted zonal biomes correspond well with existing traditional biogeographic classifications, yet some residual climatic discordance warrants further study.

Nonlinear radial envelope evolution equations and energetic particle transport in tokamak plasmas

This work provides a general description of the self-consistent energetic particle phase space transport in burning plasmas, based on nonlinear gyrokinetic theory. The self consistency is ensured by the evolution equations of the Alfvénic fluctuations by means of nonlinear radial envelope evolution equations, while energetic particle fluxes in the phase space are explicitly constructed from long-lived phase space zonal structures, which are undamped by collisionless processes. As a result, this work provides a viable route to computing fluctuation induced energetic particle transport on long time scales in realistic tokamak plasmas.

Learning how structures form in drift-wave turbulence

Drift-wave turbulence produces anomalous transport via cross-correlations between fluctuations. This transport has profound implications for confinement, structure formation, and virtually all aspects of the non-linear turbulent dynamics. In this work, we use a data-driven method based on deep learning in order to study turbulent transport in the 2D Hasegawa–Wakatani system and infer a reduced mean-field model from numerical solution. In addition to the usual turbulent diffusion, we find an effect which couples the particle flux to the local gradient of vorticity, which tends to modulate the density profile. The direct coupling to the shear is relatively weak. In addition, the deep learning method finds a model for spontaneous zonal flow generation by negative viscosity, stabilized by non-linear and hyperviscous terms. We compare these results to analytic calculations using quasilinear theory and wave kinetics, finding qualitative agreement, though the calculations miss certain higher-order effects. A simplified, 1-D model for the evolution of the profile, flow, and intensity based on the deep learning results is solved numerically and compared to previous models for staircasing based on bistability. We see that the physics uncovered by the deep learning method provided simple explanations for the formation of zonal structures in the density, flow, and turbulence fields. We highlight the important role of symmetry in the deep learning method and speculate on the portability of the method to other applications.

Solitary zonal structures in subcritical drift waves: a minimum model

Solitary zonal structures have recently been identified in gyrokinetic simulations of subcritical drift-wave (DW) turbulence with background shear flows. However, the nature of these structures has not been fully understood yet. Here, we show that similar structures can be obtained within a reduced model, which complements the modified Hasegawa–Mima equation with a generic primary instability and a background shear flow. We also find that these structures can be qualitatively reproduced in the modified Hasegawa–Wakatani equation, which subsumes the reduced model as a limit. In particular, we illustrate that in both cases, the solitary zonal structures approximately satisfy the same ‘equation of state’, which is a local relation connecting the DW envelope with the zonal-flow velocity. Due to this generality, our reduced model can be considered as a minimum model for solitary zonal structures in subcritical DWs.

Cycle Variations in the Photospheric and Interplanetary Magnetic Field and Solar Wind Parameters

The influence of cycle changes in the polar and nonpolar photospheric magnetic fields on variations in the interplanetary magnetic field (IMF) and the solar wind parameters in solar cycles 21–24 are analyzed. The results show that variations in the polar and nonpolar magnetic fields on the Carrington-rotation scales determine the parameters of the IMF and the solar wind, respectively, with the dominance of the zonal and sector structures of the global magnetic field of the Sun. The solar wind parameters exhibit a decrease in the maximum values from cycle to cycle when the sector structures dominate, while the minimum values decrease when the zonal structures dominate. This reflects a general lowing of magnitudes of both nonpolar and polar magnetic fields of the Sun observed over the last cycles. It is demonstrated that the importance of accounting for the effect of cyclic variations of the polar magnetic field on the IMF and solar wind parameters is currently underestimated.

A porous polymeric-hydroxyapatite scaffold used for femur fractures treatment: fabrication, analysis, and simulation.

One of the most common fractures in the skeleton happens in the femur. One of the important reasons for this fracture is because it is the longest bone in the body and osteoporosis affect this part a lot. The geometric complexity and anisotropy properties of this bone have received a lot of attention in the orthopedic field. In this research, a femur designed using 3D printing machine using the middle part of the hip made of polylactic acid-hydroxyapatite (PLA-HA) nanocomposite containing 0, 5, 10, 15, and 25wt% of ceramic nanoparticle. Three different types of loadings, including centralized loading, full-scale, and partially loaded, were applied to the designed femur bone. The finite element analysis was used to analyze biomechanical components. The results of the analysis showed that it is possible to use the porous scaffold model for replacement in the femur having proper strength and mechanical stability. Stress-strain analysis on femoral implant with biometric HA and PLA after modeling was performed using the finite element method under static conditions in Abaqus software. Three scaffold structures, i.e., mono-, hybrid, and zonal structures, that can be fabricated using current bioprinting techniques are also discussed with respect to scaffold design.

A flux-balanced fluid model for collisional plasma edge turbulence: Numerical simulations with different aspect ratios

We investigate the drift wave–zonal flow dynamics in a shearless slab geometry with the new flux-balanced Hasegawa-Wakatani model. As in previous Hasegawa-Wakatani models, we observe a sharp transition from a turbulence dominated regime to a zonal jet dominated regime as we decrease the plasma resistivity. However, unlike previous models, zonal structures are always present in the flux-balanced model, even for high resistivity, and strongly reduce the level of particles and vorticity flux. The more robust zonal jets also have a higher variability than in previous models, which is further enhanced when the computational domain is chosen to be elongated in the radial direction. In these cases, we observe complex multiscale dynamics, with multiple jets interacting with one another, and intermittent bursts. We present a detailed statistical analysis which highlights how the changes in the aspect ratio of the computational domain affect the third-order statistical moments, and thus modify the turbulent dynamics. By changing the aspect ratio and extending either the radial or the binormal direction, the present model study offers a better approximation to mimic turbulence in flux tube simulations for either very low magnetic shear or very high magnetic shear systems.

Quasi-biweekly oscillations in the Bay of Bengal in observations and model simulations

Intraseasonal oscillations (ISOs) significantly contribute to the variability and strength of rainfall associated with the Indian Summer Monsoon. The westward-propagating, 10–20-day, quasi-biweekly ISO (QBWISO), in association with the zonal double-cell structure, contributes to an increase in momentum and moisture from the western Pacific Ocean and South China Sea to the Bay of Bengal (BoB) and Indian subcontinent that intensifies monsoonal rainfall rates. The QBWISO also has a meridional double-cell structure positioned over 15–20°N and 0–5°N, with the northernmost cell significantly contributing to monsoonal precipitation. The atmospheric systems associated with this QBWISO, particularly the northernmost cell, induce shifts in circulation that directly impact the strength and timing of active and break monsoon periods, which are respectively characterized by wet and dry conditions. Here we conduct a multivariate analysis of the atmospheric QBWISO to both assess its overall characteristics in multiple oceanic variables and analyze how this atmospheric signal interacts with the underlying ocean. We utilize a combination of satellite observations and the Nucleus for European Modeling of the Ocean version 3.4 (NEMOv3.4) ocean model simulated temperature, salinity and mixed layer depth to examine the characteristics of QBWISO for the 2016–2018 Indian Summer Monsoon seasons. This study reveals that both the zonal and meridional double-cell structures in QBWISO precipitation are phase-locked during the southwest monsoon and positively enhance/suppress the precipitation over northern BoB leading to higher amplitudes in QBWISO sea surface salinity (SSS), compared to those in the central and southern BoB. The NEMO SSS also supports the occurrence of higher SSS anomalies at QBWISO period in the northern BoB. We find that NEMO temperature has a strong biweekly signal in the central and southern BoB down to 250 m depth, with the mixed layer temperature showing a marked decrease after the QBWISO precipitation maximum. Comparatively, at subsurface depths the QBWISO signal in NEMO salinity shows a slight increase in thermocline in the central and southern BoB, suggesting that the subsurface Arabian Sea high salinity water mass is affected by the QBWISO.

Results and prospects of geosystem monitoring in Prioksko-Terrasny biosphere reserve

The empirical-statistical models of spatial organization and function of forest biogeocoenoses of the Prioksko-Terrasny Reserve are developed. The edaphic climaxes of forest communities reflecting the diversity of zonal structures of this subtaiga region are revealed. The causal mechanisms of climax formation are described. The role of catenary organization of biogeocoenoses, as well as the lithogenic factor and the hydrological regime in the structure of forest cover is demonstrated. It is shown that the nature reserve can be a favorable testing ground for regional geosystem monitoring. However, the range of objects for solving the problems of global biosphere monitoring is very limited here due to ubiquitous forest regeneration successions. The two groups of forest biogeocoenoses are proposed as priority objects in respect to structural development and biological cycle parameters – (1) mesomorphic and meso-xeromorphic pine-lime-oak and pine-lime mixed grass and broad grass forests in a wide range of landscape interfaces (from eluvial geotopes to transaccumulative); (2) meso-hydromorphic spruce and spruce-pine acid-green forests of flat poorly drained watersheds (eluvial). This significantly diversifies the objects of geosystem monitoring.

Formation of solitary zonal structures via the modulational instability of drift waves

The dynamics of the radial envelope of a weak coherent drift-wave (DW) is approximately governed by a nonlinear Schrödinger equation (NLSE), which emerges as a limit of the modified Hasegawa–Mima equation (mHME). The NLSE has well-known soliton solutions, and its modulational instability (MI) can naturally generate solitary structures. In this paper, we demonstrate that this simple model can adequately describe the formation of solitary zonal structures in the mHME, but only when the amplitude of the coherent DW is relatively small. At larger amplitudes, the MI produces stationary zonal structures instead. Furthermore, we find that incoherent DWs with beam-like spectra can also be modulationally unstable to the formation of solitary or stationary zonal structures, depending on the beam intensity. Notably, we show that these DWs can be modeled as quantum-like particles (‘driftons’) within a recently developed phase-space (Wigner–Moyal) formulation, which intuitively depicts the solitary zonal structures as quasi-monochromatic drifton condensates. Quantum-like effects, such as diffraction, are essential to these condensates; hence, the latter cannot be described by wave-kinetic models that are based on the ray approximation.

Transient Metastability and Selective Decay for the Coherent Zonal Structures in Plasma Drift Wave Turbulence

The emergence of persistent zonal structures is studied in freely decaying plasma flows. The plasma turbulence with drift waves can be described qualitatively by the modified Hasegawa–Mima (MHM) model, which is shown to create enhanced zonal jets and more physically relevant features compared with the original Charney–Hasegawa–Mima model. We analyze the generation and stability of the zonal state in the MHM model following the strategy of the selective decay principle. The selective decay and metastable states are defined as critical points of the enstrophy at constant energy. The critical points are first shown to be invariant solutions to the MHM equation with a special emphasis on the zonal modes, but the metastable states consist of a zonal state plus drift waves with a specific smaller wavenumber. Further, it is found with full mathematical rigor that any initial state will converge to some critical point solution at the long-time limit under proper dissipation forms, while the zonal states are the only stable ones. The selective decay process of the solutions can be characterized by the transient visits to several metastable states, then the final convergence to a purely zonal state. The selective decay and metastability properties are confirmed by numerical simulations with distinct initial structures. One highlight in both theory and numerics is the tendency of Landau damping to destabilize the selective decay process.

Transport theory of phase space zonal structures

We adopt gyrokinetic theory to extract the phase space zonal structure from the flux surface averaged particle response, that is, the nonlinear response that is undamped by collisionless processes. We argue that phase space zonal structures are a proper definition for the nonlinear distortion of the plasma reference state and, thus, of the generally non-Maxwellian neighboring nonlinear equilibria consistent with toroidal symmetry breaking fluctuations. Evolution equations for phase space zonal structures are derived and discussed, along with the corresponding density and energy transport equations. It is shown that this approach is consistent with the usual evolution of macroscopic plasma profiles under the action of fluctuation induced fluxes, when the deviation of the reference state from local Maxwellian response is small. In particular, the present results recover those of a previous article [M. V. Falessi and F. Zonca, Phys. Plasmas 25, 032306 (2018)], where transport equations holding on the reference state length scale have been derived using the moment approach introduced in the classical review work by Hinton and Hazeltine.

The origin and distribution of Ordovician Yingshan dolomite on the northern slope of Tazhong area in Tarim Basin

An important exploration area of Ordovician Yingshan formation in the north Tazhong region has been demonstrated to be rich in oil and gas, especially the dolomite reservoirs in Shunnan Low Uplift and Gulong Uplift. In the study area, the dolomite interbedded with limestone decrease upward and is obviously controlled by the sedimentary facies laterally. Dolomite in the study area can be divided into two main types: fine-to-medium-grained, subhedral-to-anhedral, planar dolomite that distributed along stylolites (A1) and fine-to-medium-grained, euhedral-to-subhedral, planar sucrosic dolomite (A2). The cathodoluminescence features are recorded by common dark red light and a spot of zonal structures. The content of the oxygen isotope values and the trace elements, such as Mg, Na, Fe, and Mn, is higher in the A2 dolomite than that in A1 dolomite. Besides, the oxygen isotope values of dolomite are higher than those in limestone, which indicated that the dolomites are origin from evaporating brine. Geochemical and petrographical characteristics of Ordovician Yingshan dolomite indicated that they might be products of multi-stage dolomitization. The distribution of the sucrosic dolomite (A2) has no relationship with the third-order sequence, but coincides with the second-order sequence. It almost merely distributes in the transgressive system tracts of second-order sequence. Based on characteristics and analyses of the typical examples of single inclined platforms, the dolomite distribution of Yingshan formation is controlled by the second-order sequence in vertical, and decided by the sedimentary in horizontal. Microscopically, the grain sizes of the original sediments also work in the distribution of dolomite. The depth of water deepens as the sea-level rising, which can block the process of dolomitization. In vertical, the content of dolomite reduces upward, and in lateral, the dolomite migrates from the margin of the platform to the inner platform, showing as a regressive bed. However, dolomite that distributed along stylolites seems to be formed at shallow-burial depths.