scholarly journals The Development of a Split-tail Heliosphere and the Role of Non-ideal Processes: A Comparison of the BU and Moscow Models

2021 ◽  
Vol 923 (2) ◽  
pp. 179
Author(s):  
M. Kornbleuth ◽  
M. Opher ◽  
I. Baliukin ◽  
M. Gkioulidou ◽  
J. D. Richardson ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Solar Magnetic Field ◽  
Three Dimensional ◽  
Magnetic Field Effects ◽  
The North ◽  
Mhd Instabilities ◽  
North And South ◽  
Numerical Treatments ◽  
Numerical Approaches

Abstract Global models of the heliosphere are critical tools used in the interpretation of heliospheric observations. There are several three-dimensional magnetohydrodynamic (MHD) heliospheric models that rely on different strategies and assumptions. Until now only one paper has compared global heliosphere models, but without magnetic field effects. We compare the results of two different MHD models, the BU and Moscow models. Both models use identical boundary conditions to compare how different numerical approaches and physical assumptions contribute to the heliospheric solution. Based on the different numerical treatments of discontinuities, the BU model allows for the presence of magnetic reconnection, while the Moscow model does not. Both models predict collimation of the solar outflow in the heliosheath by the solar magnetic field and produce a split tail where the solar magnetic field confines the charged solar particles into distinct north and south columns that become lobes. In the BU model, the interstellar medium (ISM) flows between the two lobes at large distances due to MHD instabilities and reconnection. Reconnection in the BU model at the port flank affects the draping of the interstellar magnetic field in the immediate vicinity of the heliopause. Different draping in the models cause different ISM pressures, yielding different heliosheath thicknesses and boundary locations, with the largest effects at high latitudes. The BU model heliosheath is 15% thinner and the heliopause is 7% more inwards at the north pole relative to the Moscow model. These differences in the two plasma solutions may manifest themselves in energetic neutral atom measurements of the heliosphere.

A two-dimensional analysis of the compressible flow near a reconnection site at the dayside magnetopause

2007 ◽  
Vol 73 (1) ◽  
pp. 89-115 ◽  
Author(s):  
LARS G. WESTERBERG ◽  
HANS O. ÅKERSTEDT
Keyword(s):  
Magnetic Field ◽  
Transition Layer ◽  
Alfven Wave ◽  
The North ◽  
Dayside Magnetopause ◽  
Reconnection Site ◽  
Ideal Magnetohydrodynamic ◽  
North And South ◽  
Magnetic Field Variations ◽  
The Magnetic Field

Abstract.A compressible model of the magnetosheath plasma flow is considered. Magnetic reconnection is assumed to occur in a region stretching from the sub-Solar point to the north. Two locations of the reconnection site are treated: two and four Earth radii from the sub-Solar point, respectively. By treating the transition layer as very thin, we solve the governing equations approximately using the method of matched asymptotic expansions. The behavior of the magnetic field and the plasma velocity close to a reconnection site during the transition from the magnetosheath to the magnetosphere is investigated. We also obtain the development of the transition layer thickness north and south of the reconnection point. The magnetopause transition layer is represented by a large-amplitude Alfvén wave implying that the density is approximately the same across the magnetopause boundary. In order to match the solutions we consider a compressible ideal magnetohydrodynamic model describing density, velocity and magnetic field variations along the outer magnetopause boundary. We also compare the analytical results with solutions from a numerical simulation. The compressible effects on the structure of the magnetic field and the total velocity evolution are visible but not dramatic. It is shown that the transition layer north of the reconnection point is thinner than to the south. The effect is stronger for reconnection at higher latitudes.

scholarly journals Anthropocene and “Development”: Intertwined Trajectories Since the Beginning of The Great Acceleration

2020 ◽  
Vol 24 (5) ◽  
pp. 400-413
Author(s):  
Marina Dantas de Figueiredo ◽  
Fábio Freitas Schilling Marquesan ◽  
José Miguel Imas
Keyword(s):  
Developmental Model ◽  
Environmental Crisis ◽  
Environmental Consequences ◽  
The North ◽  
Development Policies ◽  
Global North ◽  
Definition Of ◽  
Great Acceleration ◽  
North And South

ABSTRACT Objectives: We aim to propose the thesis that the trajectories of the Anthropocene and the current mainstream understandings of development are intertwined from the beginning. It means that the Anthropocene and the “development” are coetaneous: the implementation of development policies for the so-considered underdeveloped regions started to happen at the same time of what is known as The Great Acceleration of production, consumption and environmental degradation in a global level. Method: In this conceptual paper, we adopt a decolonial critique as an analytical lens and argue that different geopolitical positions may be necessary for approaching the issue of the Anthropocene from epistemological reflections that can include the cultural and political context of the production and reproduction of local knowledge. Results: Our theoretical argumentation sheds light on the role of Global North and South relations in shaping the environmental crisis. Latin America (LA) exemplifies the modus operandi of the intertwinement of the practical effects of development policies and the environmental consequences underlying the Anthropocene, in which natural resources are over-explored to satisfy export-oriented trade, from the South toward the North. LA is not only a propitious context to show the validity of our thesis, but also the source of alternatives to such developmental model. Conclusion: The emphasis on development as a cause of the Anthropocene supports The Great Acceleration thesis. The proposition of the name Developmentocene comes from the thesis that development and Anthropocene are coetaneous, the intertwinement of both resulting in the very definition of the new epoch.

3D Structure of Striations in the North Pacific

2021 ◽  
Author(s):  
YU ZHANG ◽  
YU PING GUAN ◽  
RUI XIN HUANG
Keyword(s):  
North Pacific ◽  
3D Structure ◽  
Three Dimensional ◽  
Vertical Plane ◽  
Dimensional Structure ◽  
The North ◽  
Layer Analysis ◽  
Fluid Potential ◽  
The North Pacific

AbstractOcean striations are composed of alternating quasi-zonal band-like flows; this kind of organized structure of currents be found in all world’s oceans and seas. Previous studies have mainly been focused on the mechanisms of their generation and propagation. This study uses the spatial high-pass filtering to obtain the three-dimensional structure of ocean striations in the North Pacific in both the z-coordinate and σ-coordinate based on 10-yr averaged SODA3 data. First, we identify an ideal-fluid potential density domain where the striations are undisturbed by the surface forcing and boundary effects. Second, using the isopycnal layer analysis, we show that on isopycnal surfaces the orientations of striations nearly follow the potential vorticity (PV) contours, while in the meridional-vertical plane the central positions of striations are generally aligned with the latitude of zero gradient of the relative PV. Our analysis provides a simple dynamical interpretation and better understanding for the role of ocean striations.

scholarly journals Time Evolution of the Large-Scale Solar Magnetic Field

1971 ◽  
Vol 43 ◽  
pp. 588-594 ◽  
Author(s):  
Martin D. Altschuler ◽  
Gordon Newkirk ◽  
Dorothy E. Trotter ◽  
Robert Howard
Keyword(s):  
Magnetic Field ◽  
Time Evolution ◽  
Large Scale ◽  
Solar Magnetic Field ◽  
Magnetic Polarity ◽  
Zonal Harmonic ◽  
The North

The six years of data from the Mt. Wilson Magnetic Atlas were analyzed in terms of surface harmonics. Between 1959 and 1962 the dominant harmonic corresponded to a dipole lying in the plane of the equator (2 sectors). There was also a significant zonal harmonic in which both solar poles had the same magnetic polarity, opposite to that at the equator. From the end of 1962 through 1964, the harmonic corresponding to 4 sectors was dominant. In 1965 and 1966, the harmonic of the north-south dipole became significant.

scholarly journals Monitoring the Influence of the Mesoscale Ocean Dynamics on Phytoplanktonic Plumes around the Marquesas Islands Using Multi-Satellite Missions

2020 ◽  
Vol 12 (16) ◽  
pp. 2520 ◽  
Author(s):  
Angelina Cassianides ◽  
Elodie Martinez ◽  
Christophe Maes ◽  
Xavier Carton ◽  
Thomas Gorgues
Keyword(s):  
Finite Size ◽  
Ocean Dynamics ◽  
Dynamic Activity ◽  
Marquesas Islands ◽  
The North ◽  
Run Off ◽  
Dynamical Regimes ◽  
North And South

The Marquesas islands are a place of strong phytoplanktonic enhancement, whose original mechanisms have not been explained yet. Several mechanisms such as current−bathymetry interactions or island run-off can fertilize waters in the immediate vicinity or downstream of the islands, allowing phytoplankton enhancement. Here, we took the opportunity of an oceanographic cruise carried out at the end of 2018, to combine in situ and satellite observations to investigate two phytoplanktonic blooms occurring north and south of the archipelago. First, Lagrangian diagnostics show that both chlorophyll-a concentrations (Chl) plumes are advected from the islands. Second, the use of Finite-size Lyaponov Exponent and frontogenesis diagnostics reveal how the Chl plumes are shaped by the passage of a mesoscale cyclonic eddy in the south and by a converging front and finer-scale dynamic activity in the north. Our results based on these observations provide clues to the hypothesis of a fertilization from the islands themselves allowing phytoplankton to thrive. They also highlight the role of advection to disperse and shape the Chl plumes in two regions with contrasting dynamical regimes.

scholarly journals Geosynthetic reinforced column supported embankments and the role of ground improvement installation effects

2018 ◽  
Vol 55 (6) ◽  
pp. 792-809 ◽  
Author(s):  
Daniel J. King ◽  
Abdelmalek Bouazza ◽  
Joel R. Gniel ◽  
R. Kerry Rowe ◽  
Ha H. Bui
Keyword(s):  
Soil Structure ◽  
Ground Improvement ◽  
Three Dimensional ◽  
Installation Effects ◽  
Lateral Forces ◽  
Lateral Resistance ◽  
Embankment Stability ◽  
Numerical Approaches

For geosynthetic reinforced column supported embankments (GRCSE) supporting a high embankment, lateral forces associated with lateral sliding and embankment stability often govern the acceptability of a given design under serviceability conditions. Frequently, the complex soil–structure–geosynthetic interaction, the size, and the three-dimensional nature of a GRCSE necessitate the use of numerical analysis to assess embankment performance relative to serviceability criteria. However, traditional finite element method techniques used to model serviceability behaviour are limited in their ability to model the geotechnical mechanisms associated with column installation, equilibration, and group installation effects. These installation effects are examined herein based on a GRCSE field case study located in Melbourne, Australia, that has been extensively instrumented. The role that these installation effects have on the performance of the GRCSE is highlighted and the behaviour of the columns supporting the embankment is emphasized. It is shown that cracking of the unreinforced columns supporting the embankment is likely inevitable and that the reduction of lateral resistance provided by the columns should be accounted for in design. The suitability of various numerical approaches currently used in design to model the columns supporting the GRCSE, and the embankment itself, are discussed and recommendations are made.

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