scholarly journals Sheared magnetospheric plasma flows and discrete auroral arcs: a quasi-static coupling model

2007 ◽  
Vol 25 (1) ◽  
pp. 317-330 ◽  
Author(s):  
M. M. Echim ◽  
M. Roth ◽  
J. De Keyser
Keyword(s):  
Electric Potential ◽  
Large Scale ◽  
Coupling Model ◽  
Magnetospheric Plasma ◽  
Tangential Discontinuity ◽  
Topside Ionosphere ◽  
Sheared Flows ◽  
Magnetospheric Boundary ◽  
Flowing Plasma ◽  
Auroral Arcs

Abstract. We consider sheared flows in magnetospheric boundary layers of tangential discontinuity type, forming a structure that is embedded in a large-scale convergent perpendicular electric field. We construct a kinetic model that couples the magnetospheric structure with the topside ionosphere. The contribution of magnetospheric electrons and ionospheric electrons and ions is taken into account into the current-voltage relationship derived for an electric potential monotonically decreasing with the altitude. The solution of the current continuity equation gives the distribution of the ionospheric potential consistent with the given magnetospheric electric potential. The model shows that a sheared magnetospheric flow generates current sheets corresponding to upward field-aligned currents, field-aligned potential drops and narrow bands of precipitating energy, as in discrete auroral arcs. Higher velocity magnetospheric sheared flows have the tendency to produce brighter and slightly broader arcs. An increase in arc luminosity is also associated with enhancements of magnetospheric plasma density, in which case the structures are narrower. Finally, the model predicts that an increase of the electron temperature of the magnetospheric flowing plasma corresponds to slightly wider arcs but does not modify their luminosity.

scholarly journals Polar cap arcs from the magnetosphere to the ionosphere: kinetic modelling and observations by Cluster and TIMED

2012 ◽  
Vol 30 (2) ◽  
pp. 283-302 ◽  
Author(s):  
R. Maggiolo ◽  
M. Echim ◽  
C. Simon Wedlund ◽  
Y. Zhang ◽  
D. Fontaine ◽  
...  
Keyword(s):  
Energy Spectrum ◽  
Electric Field ◽  
Large Scale ◽  
Kinetic Modelling ◽  
Ion Beam ◽  
Potential Drop ◽  
Coupling Model ◽  
Optical Observations ◽  
Topside Ionosphere ◽  
Polar Cap

Abstract. On 1 April 2004 the GUVI imager onboard the TIMED spacecraft spots an isolated and elongated polar cap arc. About 20 min later, the Cluster satellites detect an isolated upflowing ion beam above the polar cap. Cluster observations show that the ions are accelerated upward by a quasi-stationary electric field. The field-aligned potential drop is estimated to about 700 V and the upflowing ions are accompanied by a tenuous population of isotropic protons with a temperature of about 500 eV. The magnetic footpoints of the ion outflows observed by Cluster are situated in the prolongation of the polar cap arc observed by TIMED GUVI. The upflowing ion beam and the polar cap arc may be different signatures of the same phenomenon, as suggested by a recent statistical study of polar cap ion beams using Cluster data. We use Cluster observations at high altitude as input to a quasi-stationary magnetosphere-ionosphere (MI) coupling model. Using a Knight-type current-voltage relationship and the current continuity at the topside ionosphere, the model computes the energy spectrum of precipitating electrons at the top of the ionosphere corresponding to the generator electric field observed by Cluster. The MI coupling model provides a field-aligned potential drop in agreement with Cluster observations of upflowing ions and a spatial scale of the polar cap arc consistent with the optical observations by TIMED. The computed energy spectrum of the precipitating electrons is used as input to the Trans4 ionospheric transport code. This 1-D model, based on Boltzmann's kinetic formalism, takes into account ionospheric processes such as photoionization and electron/proton precipitation, and computes the optical and UV emissions due to precipitating electrons. The emission rates provided by the Trans4 code are compared to the optical observations by TIMED. They are similar in size and intensity. Data and modelling results are consistent with the scenario of quasi-static acceleration of electrons that generate a polar cap arc as they precipitate in the ionosphere. The detailed observations of the acceleration region by Cluster and the large scale image of the polar cap arc provided by TIMED are two different features of the same phenomenon. Combined together, they bring new light on the configuration of the high-latitude magnetosphere during prolonged periods of Northward IMF. Possible implications of the modelling results for optical observations of polar cap arcs are also discussed.

scholarly journals A Novel Magnetosphere–Ionosphere Coupling Model for the Onset of Substrom Expansion Phase

2021 ◽  
Vol 8 ◽  
Author(s):  
P. S. Wang ◽  
L. H. Lyu
Keyword(s):  
Coupling Model ◽  
Vital Role ◽  
Expansion Phase ◽  
Magnetospheric Substorm ◽  
Hall Effects ◽  
Thin Current Sheet ◽  
Magnetospheric Boundary ◽  
E Region ◽  
Auroral Arcs ◽  
First Time

A novel magnetosphere–ionosphere (M-I) coupling model is proposed to simulate the brightening of the onset auroral arc of a magnetospheric substorm event. The new M-I coupling model is modified from the M-I coupling model proposed by the Alaska research team in 1988. We adjust the magnetospheric boundary conditions by including the Hall effects in the thin current sheet and allowing the spatial distributions of the reflection–transmission coefficient to vary with time. As a result, brightening and poleward drifting of multiple auroral arcs appear for the first time in an M-I coupling model. The new results indicate that the coupled Hall effects in the near-Earth plasma sheet and the E-region ionosphere play a vital role in triggering the onset of a magnetospheric substorm.

scholarly journals Corporate Leadership Strategy Management Based on Entropy Coupling Algorithm

2021 ◽  
Vol 2021 ◽  
pp. 1-10
Author(s):  
Zhaoyang Wu ◽  
James Yong Liao ◽  
Shiyong Wang ◽  
Jiaoyao Ji ◽  
Xiaokui Zhao
Keyword(s):  
Large Scale ◽  
Corporate Strategy ◽  
Market Competition ◽  
Coupling Model ◽  
Strategy Management ◽  
Evaluation Index System ◽  
Economic Downturn ◽  
Corporate Leadership ◽  
Leadership Strategy ◽  
Coupling Algorithm

With the continued economic downturn, coupled with the slowdown of domestic economic development and fierce market competition, the development of small and medium-sized enterprises has become more and more difficult. Because the financial background and operating strength of small and medium-sized enterprises are far inferior to large-scale enterprises, coupled with the influence of global economic integration, many small and medium-sized enterprises have gradually closed down. Therefore, exploring the entropy coupling algorithm is of great significance to the role of corporate leadership strategy management. This paper studies the coupling conditions and coupling process of corporate strategy and business model, builds a new coupling model, and goes deep into the coupling model to study the cooperation mechanism between its internal modules and initially builds the company to break through the two major dilemmas at the same time. This paper uses entropy theory to evaluate corporate leadership strategy, constructs an evaluation index system based on entropy, determines the weight of each index, and calculates the entropy value. This paper uses the alpha coefficient to test the reliability of the questionnaire. The value range of α coefficient is [0, 1], and different values represent different reliability. Large enterprises as a whole are mostly in the highly coupled (41.80%) and moderately coupled (27.34%) stages; medium-sized enterprises as a whole are mostly in the highly coupled (39.50%) and moderately coupled (31.50%) stages; small enterprises as a whole are mostly in the moderately coupled (39.50%) and moderately coupled (40.72%), low coupling (33.20%), and high coupling (25.9%) stages; microenterprises as a whole are mostly in the low coupling (43.70%), moderate coupling (36.41%), and high coupling (30.51%) stages. The results show that the entropy coupling algorithm can improve the deficiencies in the leadership strategy and provide a practical and reliable path for carrying out leadership development projects.

scholarly journals Relation of polar auroral arcs to magnetotail twisting and IMF rotation: a systematic MHD simulation study

2004 ◽  
Vol 22 (3) ◽  
pp. 951-970 ◽  
Author(s):  
A. Kullen ◽  
P. Janhunen
Keyword(s):  
Magnetic Field ◽  
Simulation Study ◽  
Large Scale ◽  
Detailed Examination ◽  
Mhd Simulation ◽  
Mhd Simulations ◽  
Sign Change ◽  
Auroral Arcs ◽  
Good Agreement ◽  
Imf Clock Angle

Abstract. We investigate with the help of a magnetohydrodynamic (MHD) model how the large-scale topology of the magnetosphere develops for a constant interplanetary magnetic field (IMF) with different IMF clock angles and for an IMF By sign change during northward IMF. A detailed examination of the topological changes in the tail and the ionosphere for different IMF conditions shows a good agreement with observational results. The MHD simulations for different constant IMF clock angle cases show the expected field-line bending and tail twisting for nonzero IMF By. The tail becomes longer and at its tailward end stronger twisted for IMF Bz>∣By∣ than for IMF Bz

scholarly journals APPLICATION OF LES-STOCHASTIC TWO-WAY MODEL TO TWO-PHASE BOUNDARY LAYER FLOWS

2011 ◽  
Vol 1 (32) ◽  
pp. 5
Author(s):  
Yasunori Watanabe ◽  
Yuta Mitobe ◽  
Yasuo Niida ◽  
Ayumi Saruwatari
Keyword(s):  
Boundary Layer ◽  
Particle Size ◽  
Large Scale ◽  
Three Dimensional ◽  
Coupling Model ◽  
Turbulent Energy ◽  
Boundary Layer Flows ◽  
Two Phase ◽  
Eddy Simulation ◽  
Suspension Process

A particle / turbulence two-way coupling model, integrated with conventional stochastic and sub-grid stress models of three-dimensional Large Eddy Simulation (LES), has been applied to the particle-laden turbulent flow in a wave boundary layer developed over seabed with the aim to understand dynamic effects of the particle size and number density to the suspension process in shearing flow over the seabed. While the particle size affects local velocity fluctuations, the particle population significantly induces secondary large-scale flows varying over a scale of the wavelength, and intensifies the turbulent energy near the bed. The particle-induced turbulence may result in additional suspension from the bed, causing a recursive suspension process via the particle turbulence interaction in the boundary layer.

scholarly journals Three-Dimensional Numerical Modeling of Large-Scale Free Surface Flows with Heat and Contaminant Transfer in Reservoirs

2021 ◽  
Vol 2021 ◽  
pp. 1-17
Author(s):  
Wei Diao ◽  
Hao Yuan ◽  
Liang Chen ◽  
Xujin Zhang ◽  
Cunze Zhang
Keyword(s):  
Free Surface ◽  
Large Scale ◽  
Three Dimensional ◽  
Coupling Model ◽  
Free Surface Flows ◽  
Surface Flows ◽  
Scale Free ◽  
Pollutant Distribution ◽  
Contaminant Transfer ◽  
Double Diffusive

The temperature distribution and pollutant distribution in large reservoirs have always been a hotspot in the field of hydraulics and environmentology, and the three-dimensional numerical modeling that can effectively simulate the interactions between the temperature fields, concentration fields, and flow fields needs to be proposed. The double-diffusive convection lattice Boltzmann method is coupled with a single-phase volume of fluid model for simulating heat and contaminant transfer in large-scale free surface flows. The coupling model is used to simulate the double-diffusive natural convection in a cubic cavity and the temperature distribution of a model reservoir. The mechanism of convection-diffusion, gravity sinking flow, and the complexity of the temperature and the pollutant redistribution process are analyzed. Good agreements between the simulated results and the reference data validate the accuracy and effectiveness of the proposed coupling model in studying free surface flows with heat and contaminant transfer. At last, the temporal and spatial variations of flow state, water temperature stratification, and pollutant transport in the up-reservoir of a pumped-storage power station are simulated and analyzed by the proposed model. The obtained variations of the flow field agree well with the observations in the physical model test and in practical engineering. In addition, the simulated temperature field and concentration field are also consistent with the general rules, which demonstrates the feasibility of the coupling model in simulating temperature and pollutant distribution problems in realistic reservoirs and shows its good prospects in engineering application.

Adaptive Control of Large-Scale Soft Robot Manipulators With Unknown Payloads

2019 ◽  
Author(s):  
Jonathan S. Terry ◽  
Justin Whitaker ◽  
Randal W. Beard ◽  
Marc D. Killpack
Keyword(s):  
Adaptive Control ◽  
Large Scale ◽  
Robot Manipulator ◽  
Coupling Model ◽  
Effective Control ◽  
Soft Robot ◽  
Soft Robots ◽  
Pneumatic Actuators ◽  
Integral Controller ◽  
Model Reference Adaptive

Abstract The compliance and other nonlinear dynamics of large-scale soft robots makes effective control difficult. This is especially true when working with unknown payloads or when the system dynamics change over time which is likely to happen for soft robots. In this paper, we present a novel method of coupling model reference adaptive control (MRAC) with model predictive control (MPC) for platforms with antagonistic pneumatic actuators. We demonstrate its utility on a fully inflatable, six degree-of-freedom pneumatically actuated soft robot manipulator that is over two meters long. Specifically, we compare control performance with no integral controller, with an integral controller, and with MRAC when running a nominal model predictive controller with significant weight attached to the end effector.

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