scholarly journals Network community structure of substorms using SuperMAG magnetometers

2021 ◽  
Vol 12 (1) ◽  
Author(s):  
L. Orr ◽  
S. C. Chapman ◽  
J. W. Gjerloev ◽  
W. Guo
Keyword(s):  
Large Scale ◽  
Three Dimensional ◽  
Easy Access ◽  
Directed Network ◽  
Coherent System ◽  
Dimensional System ◽  
Ionospheric Currents ◽  
Substorm Current Wedge ◽  
Spatially Extended ◽  
Current Wedge

AbstractGeomagnetic substorms are a global magnetospheric reconfiguration, during which energy is abruptly transported to the ionosphere. Central to this are the auroral electrojets, large-scale ionospheric currents that are part of a larger three-dimensional system, the substorm current wedge. Many, often conflicting, magnetospheric reconfiguration scenarios have been proposed to describe the substorm current wedge evolution and structure. SuperMAG is a worldwide collaboration providing easy access to ground based magnetometer data. Here we show application of techniques from network science to analyze data from 137 SuperMAG ground-based magnetometers. We calculate a time-varying directed network and perform community detection on the network, identifying locally dense groups of connections. Analysis of 41 substorms exhibit robust structural change from many small, uncorrelated current systems before substorm onset, to a large spatially-extended coherent system, approximately 10 minutes after onset. We interpret this as strong indication that the auroral electrojet system during substorm expansions is inherently a large-scale phenomenon and is not solely due to many meso-scale wedgelets.

scholarly journals A Multidimensional and Multiscale Model for Pressure Analysis in a Reservoir-Pipe-Valve System

2019 ◽  
Vol 141 (5) ◽  
Author(s):  
Feng Jie Zheng ◽  
Chao Yong Zong ◽  
William Dempster ◽  
Fu Zheng Qu ◽  
Xue Guan Song
Keyword(s):  
Large Scale ◽  
Pressure Fluctuations ◽  
Three Dimensional ◽  
Multiscale Model ◽  
Computational Time ◽  
Small Scale ◽  
Dimensional System ◽  
Cfd Model ◽  
Computationally Efficient ◽  
Proposed Model

Reservoir-pipe-valve (RPV) systems are widely used in many industrial processes. The pressure in an RPV system plays an important role in the safe operation of the system, especially during the sudden operations such as rapid valve opening or closing. To investigate the pressure response, with particular interest in the pressure fluctuations in an RPV system, a multidimensional and multiscale model combining the method of characteristics (MOC) and computational fluid dynamics (CFD) method is proposed. In the model, the reservoir is modeled as a zero-dimensional virtual point, the pipe is modeled as a one-dimensional system using the MOC, and the valve is modeled using a three-dimensional CFD model. An interface model is used to connect the multidimensional and multiscale model. Based on the model, a transient simulation of the turbulent flow in an RPV system is conducted in which not only the pressure fluctuation in the pipe but also the detailed pressure distribution in the valve is obtained. The results show that the proposed model is in good agreement when compared with a high fidelity CFD model used to represent both large-scale and small-scale spaces. As expected, the proposed model is significantly more computationally efficient than the CFD model. This demonstrates the feasibility of analyzing complex RPV systems within an affordable computational time.

scholarly journals Relative contributions of large-scale and wedgelet currents in the substorm current wedge

2020 ◽  
Vol 72 (1) ◽  
Author(s):  
Y. Nishimura ◽  
L. R. Lyons ◽  
C. Gabrielse ◽  
J. M. Weygand ◽  
E. F. Donovan ◽  
...  
Keyword(s):  
Large Scale ◽  
Substorm Current Wedge ◽  
Current Wedge

Three-Dimensional Simulations of Phase Separation in Model Binary Alloy Systems with Elasticity

1997 ◽  
Vol 481 ◽  
Author(s):  
D. Orlikowski ◽  
C. Sagui ◽  
A. S. Somoza ◽  
C. Roland
Keyword(s):  
Phase Separation ◽  
Binary Alloy ◽  
Large Scale ◽  
Three Dimensional ◽  
Elastic Field ◽  
Dimensional System ◽  
Elastic Fields ◽  
Slowing Down ◽  
Three Dimensional Simulations ◽  
Alloy Systems

ABSTRACTWe report on large-scale three-dimensional simulations of phase separation in model binary alloy systems in the presence of elastic fields. The elastic field has several important effects on the morphology of the system: the ordered domains are subject to shape transformations, and spatial ordering. In contrast to two-dimensional system, no significant slowing down in the growth is observed. There is also no evidence of any “reverse coarsening” of the domains.

scholarly journals Substorm behavior of the auroral electrojet indices

2004 ◽  
Vol 22 (6) ◽  
pp. 2135-2149 ◽  
Author(s):  
J. W. Gjerloev ◽  
R. A. Hoffman ◽  
M. M. Friel ◽  
L. A. Frank ◽  
J. B. Sigwarth
Keyword(s):  
Current System ◽  
Three Dimensional ◽  
Recovery Phase ◽  
Auroral Electrojet ◽  
Spatial Behavior ◽  
Early Recovery ◽  
Substorm Current Wedge ◽  
Expansion Phase ◽  
Systematic Behavior ◽  
Current Wedge

Abstract. The behavior of the auroral electrojet indices AU and AL during classical substorms is investigated by the use of global auroral images. A superposition of the 12 AE stations onto global auroral images and identification of the AL and AU contributing stations enable an understanding of the temporal as well as spatial behavior of the indices with respect to the substorm coordinate system and timeframe. Based on this simple technique it was found that at substorm onset the AL contributing station makes a characteristic jump from a location near the dawn terminator to the onset region, typically bypassing one or more AE stations. During the expansion phase this station typically lies at the poleward edge of the surge region. This is the location of the intense substorm current wedge electrojet in the semiempirical self-consistent substorm model of the three-dimensional current system by Gjerloev and Hoffman (2002). This current wedge is fed primarily pre-midnight by an imbalance of the Region 0 and Region 1 field-aligned currents, not from the dawnside westward electrojet. Then during the early recovery phase the AL contributing station jumps back to the dawn sector. The defining AU station does not show any similar systematic behavior. We also find that the dawn side westward electrojet seems to be unaffected by the introduction of the substorm current wedge. According to our model, much of this current is closed to the magnetosphere as it approaches midnight from dawn. Based on the characteristics of the AL station jumps, the behavior of the dawn-side electrojet, and the understanding of the three-dimensional substorm current system from our model, we provide additional experimental evidence for, and an understanding of, the concept of the two component westward electrojet, as suggested by Kamide and Kokubun (1996).

Thermal Stress of Through Silicon Vias and Si Chips in 3D SiP

2011 ◽  
Author(s):  
Takahiro Kinoshita ◽  
Takashi Kawakami ◽  
Tatsuhiro Hori ◽  
Keiji Matsumoto ◽  
Sayuri Kohara ◽  
...  
Keyword(s):  
Single Crystals ◽  
Yield Stress ◽  
Thermal Conduction ◽  
Large Scale ◽  
Thermal Stresses ◽  
Equivalent Stress ◽  
Three Dimensional ◽  
Dimensional System ◽  
Silicon Vias ◽  
Three Dimensional System

Thermal conduction and mechanical strength around TSV (Through Silicon Via) structures of 3D SiP (Three Dimensional System in Package) were discussed both cases of with and without void in TSV by using a large scale simulator based on FEM, ADVENTURECluster® for ensuring the reliability of 3D SiP. In the results, the thermal performance that was required in 3D SiP was estimated to ensure the reliability. Simulations for thermal stresses around TSV structure in 3D SiP under thermal cycle condition due to power ON/OFF were carried out. In case that void was not in TSV, stresses in TSV were close to hydrostatic pressure and the magnitude of the equivalent stress was lower than the yield stress of copper. However, the level of the stresses, especially in Si chips, should not be negligible in inducing damages to TSVs and Si single crystals. In case that void was in TSV, stress was concentrated around void in TSV and the magnitude of the equivalent stress was lower than the yield stress of copper. The level of stresses applied to Si chip was slightly reduced due to void in TSV. However, its level should not be negligible in inducing damages to TSVs and Si single crystals.

scholarly journals Creation of the substorm current wedge through the perturbation of the directly driven current system: a new model for substorm expansion

2005 ◽  
Vol 23 (6) ◽  
pp. 2171-2182 ◽  
Author(s):  
G. Rostoker ◽  
E. Friedrich
Keyword(s):  
Current System ◽  
Three Dimensional ◽  
Magnetospheric Substorms ◽  
Substorm Current Wedge ◽  
System A ◽  
Storms And Substorms ◽  
Auroral Phenomena ◽  
Current Systems ◽  
System Operating ◽  
Current Wedge

Abstract. The past four decades have seen a considerable amount of research on the study of magnetospheric substorms, and over most of these years the expansive phase of the substorm has been associated with the development of a three dimensional current system that has been termed the substorm current wedge. This current system has been thought to be a consequence of the short-circuiting of crosstail current through the ionosphere, and is viewed as a distinctive current system operating independently from the directly driven current with which it co-exists. The purpose of this paper is to show that the substorm current wedge should be viewed as an equivalent current system rather than a real current system. It will be shown that the magnetic perturbation pattern associated with the current wedge can be modeled as purely a perturbation of the directly driven current system in the midnight sector. Keywords. Magnetospheric physics (Auroral phenomena; Current systems; Magnetotail; Storms and substorms

On the measurement of the turbulent diffusivity of a large-scale magnetic field

2013 ◽  
Vol 717 ◽  
pp. 347-360 ◽  
Author(s):  
S. M. Tobias ◽  
F. Cattaneo
Keyword(s):  
Magnetic Field ◽  
Large Scale ◽  
Laboratory Experiments ◽  
Three Dimensional ◽  
Effective Diffusivity ◽  
Dimensional System ◽  
Two Dimensional ◽  
Electrically Conducting ◽  
State Response ◽  
Large Scale Magnetic Field

AbstractWe argue that a method developed by Ångström (Ann. Phys. Chem., vol. 114, 1861, pp. 513–530) to measure the thermal conductivity of solids can be adapted to determine the effective diffusivity of a large-scale magnetic field in a turbulent electrically conducting fluid. The method consists of applying an oscillatory source and measuring the steady-state response. We illustrate this method in a two-dimensional system. This geometry is chosen because it is possible to compare the results with independent methods that are restricted to two-dimensional flows. We describe two variants of this method: one (the ‘turbulent Ångström method’) that is better suited to laboratory experiments and a second (the ‘method of oscillatory sines’) that is effective for numerical experiments. We show that, if correctly implemented, all methods agree. Based on these results we argue that these methods can be extended to three-dimensional numerical simulations and laboratory experiments.

Thermal Stress Simulation for 3D SiP With TSV Structure Under Unsteady Thermal Loads

2015 ◽  
Author(s):  
Takahiro Kinoshita ◽  
Takashi Kawakami ◽  
Tomoya Sugiura ◽  
Keiji Matsumoto ◽  
Sayuri Kohara ◽  
...  
Keyword(s):  
Heat Generation ◽  
Large Scale ◽  
Hot Spot ◽  
Three Dimensional ◽  
Thermal Conditions ◽  
Local Area ◽  
Dimensional System ◽  
Thermal Loads ◽  
Temperature Elevation ◽  
3D Packaging

3D packaging technology and TSV (Through Silicon Via) technology have been developed to reduce size and improve performance of semiconductor devices. On the other hand, cooling performance is decreased because thermal sources are accumulated and concentrated by chip stacking. In particular, unsteady thermal loads by hot spot, which is steep temperature elevation within a local area, produce damage in stacked semiconductor chips. In this study, temperature elevation in stacked chips and stresses around TSV structure in 3D SiP (Three Dimensional System in Package) are discussed with a large scale and a parallel computing simulator, which was based on FEM (Finite Element Method), under unsteady thermal conditions as hot spot. The level of heat generation was varied and conditions for device operation were suggested. In addition, stresses of Cu-TSV and Si chips are discussed as function of level of heat generation by hot spot to ensure the reliability of 3D SiP.

scholarly journals A Review on Additive Manufacturing Possibilities for Electrical Machines

Energies ◽  
2021 ◽  
Vol 14 (7) ◽  
pp. 1940
Author(s):  
Muhammad Usman Naseer ◽  
Ants Kallaste ◽  
Bilal Asad ◽  
Toomas Vaimann ◽  
Anton Rassõlkin
Keyword(s):  
Additive Manufacturing ◽  
Large Scale ◽  
Three Dimensional ◽  
Electrical Machines ◽  
Electromagnetic Properties ◽  
Scale Production ◽  
Performance Parameters ◽  
Large Scale Production ◽  
One Step ◽  
Manufacturing Techniques

This paper presents current research trends and prospects of utilizing additive manufacturing (AM) techniques to manufacture electrical machines. Modern-day machine applications require extraordinary performance parameters such as high power-density, integrated functionalities, improved thermal, mechanical & electromagnetic properties. AM offers a higher degree of design flexibility to achieve these performance parameters, which is impossible to realize through conventional manufacturing techniques. AM has a lot to offer in every aspect of machine fabrication, such that from size/weight reduction to the realization of complex geometric designs. However, some practical limitations of existing AM techniques restrict their utilization in large scale production industry. The introduction of three-dimensional asymmetry in machine design is an aspect that can be exploited most with the prevalent level of research in AM. In order to take one step further towards the enablement of large-scale production of AM-built electrical machines, this paper also discusses some machine types which can best utilize existing developments in the field of AM.

Sign in / Sign up

Export Citation Format

Share Document