scholarly journals Plasma flow channels with ULF waves observed by Cluster and Double Star

2005 ◽  
Vol 23 (8) ◽  
pp. 2929-2935 ◽  
Author(s):  
M. Volwerk ◽  
T. L. Zhang ◽  
R. Nakamura ◽  
A. Runov ◽  
W. Baumjohann ◽  
...  
Keyword(s):  
Magnetic Structure ◽  
Plasma Flow ◽  
Large Scale ◽  
Double Star ◽  
Flow Channel ◽  
Propagation Direction ◽  
Ulf Waves ◽  
Flow Channels ◽  
Earthward Flow

Abstract. On 14 August 2004 a large-scale magnetic structure was observed by Double Star TC-1 in the southern lobe and by Cluster in the northern lobe of the magnetotail. The structure has the signature of a (localized) dipolarization, decreasing Bx accompanied by an increasing Bz and a strong earthward flow. The propagation direction of this structure, however, seems to be more in the dawnward direction than earthward. The structure is accompanied by ULF waves with a period of ~5 min, which are simultaneously observed by the ground magnetometer station DIK, at the magnetic footpoints of the spacecraft. We interprete these waves as modes driven by the plasma flow and propagating in the flow channel.

scholarly journals Remarkable Symmetries in the Milky Way Disc's Magnetic Field

2011 ◽  
Vol 28 (2) ◽  
pp. 171-176 ◽  
Author(s):  
P. P. Kronberg ◽  
K. J. Newton-McGee
Keyword(s):  
Magnetic Structure ◽  
Large Scale ◽  
Milky Way ◽  
Galactic Center ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Field Structure ◽  
Field Pattern ◽  
Close Coupling ◽  
Sign Change

AbstractWe apply a new, expanded compilation of extragalactic source Faraday rotation measures (RM) to investigate the broad underlying magnetic structure of the Galactic disk at latitudes ∣b∣ ≲15° over all longitudes l, where our total number of RMs is comparable to those in the combined Canadian Galactic Plane Survey (CGPS) at ∣b∣ < 4° and the Southern Galactic Plane (SGPS) ∣b∣<1.5°. We report newly revealed, remarkably coherent patterns of RM at ∣b∣≲15° from l∼270° to ∼90° and RM(l) features of unprecedented clarity that replicate in l with opposite sign on opposite sides of the Galactic center. They confirm a highly patterned bisymmetric field structure toward the inner disc, an axisymmetic pattern toward the outer disc, and a very close coupling between the CGPS/SGPS RMs at ∣b∣≲3° (‘mid-plane’) and our new RMs up to ∣b∣∼15° (‘near-plane’). Our analysis also shows the vertical height of the coherent component of the disc field above the Galactic disc's mid-plane—to be ∼1.5 kpc out to ∼6 kpc from the Sun. This identifies the approximate height of a transition layer to the halo field structure. We find no RM sign change across the plane within ∣b∣∼15° in any longitude range. The prevailing disc field pattern and its striking degree of large-scale ordering confirm that our side of the Milky Way has a very organized underlying magnetic structure, for which the inward spiral pitch angle is 5.5°±1° at all ∣b∣ up to ∼12° in the inner semicircle of Galactic longitudes. It decreases to ∼0° toward the anticentre.

Crack Growth and Propagation in Metallic Alloys

1995 ◽  
Vol 409 ◽  
Author(s):  
W. C. Morrey ◽  
L. T. Wille
Keyword(s):  
Large Scale ◽  
Critical Strain ◽  
Cleavage Plane ◽  
Crack Tip ◽  
Metallic Alloys ◽  
Propagation Direction ◽  
Dynamics Simulation ◽  
Parallel Computer ◽  
Massively Parallel ◽  
Tip Position

AbstractUsing large-scale molecular dynamics simulation on a massively parallel computer, we have studied the initiation of cracking in a Monel-like alloy of Cu-Ni. In a low temperature 2D sample, fracture from a notch starts at a little beyond 2.5% critical strain when the propagation direction is perpendicular to a cleavage plane. We discuss a method of characterizing crack tip position using a measure of area around the crack tip.

scholarly journals The magnetic structure of our Galaxy: a review of observations

2008 ◽  
Vol 4 (S259) ◽  
pp. 455-466 ◽  
Author(s):  
JinLin Han
Keyword(s):  
Magnetic Fields ◽  
Magnetic Structure ◽  
Large Scale ◽  
Galactic Halo ◽  
Galactic Center ◽  
Galactic Plane ◽  
Galactic Disk ◽  
Dust Emission ◽  
Measure Data ◽  
Radio Sources

AbstractThe magnetic structure in the Galactic disk, the Galactic center and the Galactic halo can be delineated more clearly than ever before. In the Galactic disk, the magnetic structure has been revealed by starlight polarization within 2 or 3 kpc of the Solar vicinity, by the distribution of the Zeeman splitting of OH masers in two or three nearby spiral arms, and by pulsar dispersion measures and rotation measures in nearly half of the disk. The polarized thermal dust emission of clouds at infrared, mm and submm wavelengths and the diffuse synchrotron emission are also related to the large-scale magnetic field in the disk. The rotation measures of extragalactic radio sources at low Galactic latitudes can be modeled by electron distributions and large-scale magnetic fields. The statistical properties of the magnetized interstellar medium at various scales have been studied using rotation measure data and polarization data. In the Galactic center, the non-thermal filaments indicate poloidal fields. There is no consensus on the field strength, maybe mG, maybe tens of μG. The polarized dust emission and much enhanced rotation measures of background radio sources are probably related to toroidal fields. In the Galactic halo, the antisymmetric RM sky reveals large-scale toroidal fields with reversed directions above and below the Galactic plane. Magnetic fields from all parts of our Galaxy are connected to form a global field structure. More observations are needed to explore the untouched regions and delineate how fields in different parts are connected.

scholarly journals Intelligent Design Optimization System for Additively Manufactured Flow Channels Based on Fluid–Structure Interaction

Micromachines ◽  
2022 ◽  
Vol 13 (1) ◽  
pp. 100
Author(s):  
Haonan Ji ◽  
Bin Zou ◽  
Yongsheng Ma ◽  
Carlos F. Lange ◽  
Jikai Liu ◽  
...  
Keyword(s):  
Design Optimization ◽  
Intelligent Design ◽  
Fluid Structure Interaction ◽  
Parametric Modeling ◽  
Flow Channel ◽  
Design Parameters ◽  
Fluid Structure ◽  
Structure Interaction ◽  
Optimization System ◽  
Flow Channels

Based on expert system theory and fluid–structure interaction (FSI), this paper suggests an intelligent design optimization system to derive the optimal shape of both the fluid and solid domain of flow channels. A parametric modeling scheme of flow channels is developed by design for additive manufacturing (DfAM). By changing design parameters, a series of flow channel models can be obtained. According to the design characteristics, the system can intelligently allocate suitable computational models to compute the flow field of a specific model. The pressure-based normal stress is abstracted from the results and transmitted to the solid region by the fluid–structure (FS) interface to analyze the strength of the structure. The design space is obtained by investigating the simulation results with the metamodeling method, which is further applied for pursuing design objectives under constraints. Finally, the improved design is derived by gradient-based optimization. This system can improve the accuracy of the FSI simulation and the efficiency of the optimization process. The design optimization of a flow channel in a simplified hydraulic manifold is applied as the case study to validate the feasibility of the proposed system.

Triple-Dipole Model on the Large-Scale Magnetic Structure of the Sun

1996 ◽  
pp. 623-625
Author(s):  
T. Saito ◽  
Y. Kozuka ◽  
M. Kojima ◽  
Y. Mori ◽  
M. Yasue ◽  
...  
Keyword(s):  
Magnetic Structure ◽  
Large Scale ◽  
Dipole Model ◽  
The Sun

scholarly journals Numerical investigation on the characteristics of water transfer in PEMFC with bionic flow channel

2019 ◽  
Vol 83 ◽  
pp. 01005
Author(s):  
Tao Chen ◽  
Shihua Liu ◽  
Li Yang
Keyword(s):  
Water Transport ◽  
Polymer Electrolyte Membrane ◽  
Flow Channel ◽  
Water Drainage ◽  
Transmission Characteristics ◽  
Electrolyte Membrane ◽  
Numerical Studies ◽  
Flow Channels ◽  
Significant Difference ◽  
Different Types

The content and the transmission characteristics of the water in the polymer electrolyte membrane fuel cell (PEMFC) have a significant influence on its performance. So far, there are few separate numerical studies on the process of water transport in the bionic flow channel, and the performance of bionic flow channel is different from conventional flow channel in part owing to the differences of their water drainage. Therefore, in order to understand the water drainage process of bionic flow channel, two different types of bionic flow channels are adopted in this paper. The method of numerical simulation is used to study the transmission process of liquid water in the bionic flow channel of different placement orientations. The simulation results found that the orientations of bionic flow channel has an influence on the process of water transport in the flow channel, and the process of water drainage also has a significant difference in the two different types of bionic flow channel.

scholarly journals Observation of reconnection pulses by Cluster and Double Star

2005 ◽  
Vol 23 (8) ◽  
pp. 2921-2927 ◽  
Author(s):  
X. H. Deng ◽  
R. X. Tang ◽  
R. Nakamura ◽  
W. Baumjohann ◽  
T. L. Zhang ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Energetic Electron ◽  
Curvature Vector ◽  
Double Star ◽  
Neutral Sheet ◽  
Inner Magnetosphere ◽  
Point Analysis ◽  
Earthward Flow ◽  
Tailward Flow ◽  
The Magnetic Field

Abstract. During a reconnection event on 7 August 2004, Cluster and Double Star (TC-1) were near the neutral sheet and simultaneously detected the signatures of the reconnection pulses. AT 22:59 UT tailward flow followed by earthward flow was detected by Cluster at about 15 RE, while earthward plasma flow followed by tailward flow was observed by TC-1 at about 10 RE. During the flow reversal from tailward to earthward, the magnetic field Bz changed sign from mainly negative values to positive, and the X component of the magnetic curvature vector switched sign from the tailward direction to the earthward direction, which indicates that the reconnection site (X-line) moved tailward past the Cluster constellation. By using multi-point analysis and observation of energetic electron and ion flux, we study the movement and structure of the current sheet and discuss the braking effect of the earthward flow bursts in the inner magnetosphere.

scholarly journals Cluster and Double Star observations of dipolarization

2005 ◽  
Vol 23 (8) ◽  
pp. 2915-2920 ◽  
Author(s):  
R. Nakamura ◽  
W. Baumjohann ◽  
T. L. Zhang ◽  
C. M. Carr ◽  
A. Balogh ◽  
...  
Keyword(s):  
Local Time ◽  
Double Star ◽  
Propagation Direction ◽  
Dissipation Process ◽  
Analysis Techniques ◽  
Point Analysis ◽  
Time Sector ◽  
Local Time Sector ◽  
The Imf

Abstract. We studied two types of dipolarization events with different IMF conditions when Cluster and Double Star (TC-1) were located in the same local time sector: 7 August 2004, 18:00-24:00 UT, during a disturbed southward/northward IMF interval, and 14 August 2004, 21:00-24:00 UT, when the IMF was stably northward. Cluster observed dipolarization as well as fast flows during both intervals, but this was not the case for TC-1. For both events the satellites crossed near the conjugate location of the MIRACLE stations. By using multi-point analysis techniques, the direction/speed of the propagation is determined using Cluster and is then compared with the disturbances at TC-1 to discuss its spatial/temporal scale. The propagation direction of the BZ disturbance at Cluster was mainly dawnward with a tailward component for 7 August and with a significant Earthward component for 14 August associated with fast flows. We suggest that the role of the midtail fast flows can be quite different in the dissipation process depending on the condition of the IMF and resultant configuration of the tail.

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