scholarly journals Multiple magnetic dipolarizations observed by THEMIS during a substorm

2011 ◽  
Vol 29 (2) ◽  
pp. 331-339 ◽  
Author(s):  
S. P. Duan ◽  
Z. X. Liu ◽  
J. Liang ◽  
Y. C. Zhang ◽  
T. Chen
Keyword(s):  
Plasma Sheet ◽  
High Speed ◽  
Onset Time ◽  
Substorm Onset ◽  
Bulk Flow ◽  
Small Scale ◽  
Expansion Phase ◽  
Ae Index ◽  
The Magnetic Field ◽  
Bulk Speed

Abstract. The magnetic field dipolarization in the vicinity of substorm onset and during substorm expansion phase during the period of 06:00–06:40 UT on 15 February 2008 is investigated with observations from multiple probes of THEMIS. It is found that the magnetic dipolarization at the substorm onset (the onset time was about 06:14 UT) was not accompanied by obvious magnetic disturbance and ion bulk speed variation. The magnetic dipolarizations taking place during the substorm expansion phase observed by P4~(−10.97, 2.04, −3.03) RE and P3~(−11.32, 1.15, −3.10) RE were mostly accompanied by high speed earthward ion bulk flow, but the magnetic dipolarizations occurring during the substorm expansion phase observed by P5~(−9.45, 1.07, −2.85) RE were not accompanied by high speed earthward ion bulk flow. Before substorm onset THEMIS P3, P4, P5 all observed the Bx component fluctuation with a period of about 300 s. After substorm onset earthward high speed ion bulk flow and significant magnetic disturbances both occurred at P3 and P4 locations. These results indicate that there is no one-to-one relationship between the near-Earth magnetic dipolarization and the earthward ion bulk flow. In particular, the magnetic dipolarization occurring on the earthward side of the inner near-Earth plasma sheet is not accompanied by high speed earthward ion bulk flow. The dipolarization at substorm onset is a local and small scale phenomenon. There are multiple magnetic dipolarizations occurring during the substorm expansion phase. The dipolarization process is very complex and is not simply an MHD process. It is accompanied by some kinds of plasma instabilities, the plasma sheet azimuthal expansion not only by earthward ion bulk flow during substorm. A sharp increase of the AE index does not always give an accurate substorm onset time for substorm analysis.

scholarly journals Bi-directional electrons in the near-Earth plasma sheet

2003 ◽  
Vol 21 (7) ◽  
pp. 1497-1507 ◽  
Author(s):  
K. Shiokawa ◽  
W. Baumjohann ◽  
G. Paschmann
Keyword(s):  
Magnetic Field ◽  
Plasma Sheet ◽  
High Speed ◽  
Elevation Angle ◽  
Occurrence Rate ◽  
Neutral Sheet ◽  
Magnetospheric Configuration And Dynamics ◽  
Central Plasma ◽  
Occurrence Characteristics ◽  
The Magnetic Field

Abstract. We have studied the occurrence characteristics of bi-directional electron pitch angle anisotropy (enhanced flux in field-aligned directions, F^ /F|| > 1.5) at energies of 0.1–30 keV using plasma and magnetic field data from the AMPTE/IRM satellite in the near-Earth plasma sheet. The occurrence rate increases in the tailward direction from XGSM = - 9 RE to - 19 RE . The occurrence rate is also enhanced in the midnight sector, and furthermore, whenever the elevation angle of the magnetic field is large while the magnetic field intensity is small, B ~ 15 nT. From these facts, we conclude that the bi-directional electrons in the central plasma sheet are produced mainly in the vicinity of the neutral sheet and that the contribution from ionospheric electrons is minor. A high occurrence is also found after earthward high-speed ion flows, suggesting Fermi-type field-aligned electron acceleration in the neutral sheet. Occurrence characteristics of bi-directional electrons in the plasma sheet boundary layer are also discussed.Key words. Magnetospheric physics (magnetospheric configuration and dynamics; magnetotail; plasma sheet)

scholarly journals Multi-instrument observations of the ionospheric counterpart of a bursty bulk flow in the near-Earth plasma sheet

2004 ◽  
Vol 22 (4) ◽  
pp. 1061-1075 ◽  
Author(s):  
A. Grocott ◽  
T. K. Yeoman ◽  
R. Nakamura ◽  
S. W. H. Cowley ◽  
H. U. Frey ◽  
...  
Keyword(s):  
Plasma Sheet ◽  
Large Scale ◽  
Current System ◽  
Global Scale ◽  
Bulk Flow ◽  
Optical Data ◽  
Small Scale ◽  
Plasma Convection ◽  
Bursty Bulk Flow ◽  
Central Plasma

Abstract. On 07 September 2001 the Cluster spacecraft observed a "bursty bulk flow" event in the near-Earth central plasma sheet. This paper presents a detailed study of the coincident ground-based observations and attempts to place them within a simple physical framework. The event in question occurs at ~22:30 UT, some 10min after a southward turning of the IMF. IMAGE and SAMNET magnetometer measurements of the ground magnetic field reveal perturbations of a few tens of nT and small amplitude Pi2 pulsations. CUTLASS radar observations of ionospheric plasma convection show enhanced flows out of the polar cap near midnight, accompanied by an elevated transpolar voltage. Optical data from the IMAGE satellite also show that there is a transient, localised ~1 kR brightening in the UV aurora. These observations are consistent with the earthward transport of plasma in the tail, but also indicate the absence of a typical "large-scale" substorm current wedge. An analysis of the field-aligned current system implied by the radar measurements does suggest the existence of a small-scale current "wedgelet", but one which lacks the global scale and high conductivities observed during substorm expansions. Key words. Ionosphere (auroral ionosphere; ionospheremagnetosphere interactions; plasma convection)

scholarly journals Survey of large-amplitude flapping motions in the midtail current sheet

2006 ◽  
Vol 24 (7) ◽  
pp. 2015-2024 ◽  
Author(s):  
V. A. Sergeev ◽  
D. A. Sormakov ◽  
S. V. Apatenkov ◽  
W. Baumjohann ◽  
R. Nakamura ◽  
...  
Keyword(s):  
Current Sheet ◽  
High Speed ◽  
Radial Distance ◽  
Statistical Distributions ◽  
Expansion Phase ◽  
Success Criteria ◽  
Cluster Data ◽  
Ae Index ◽  
Activity Dependence ◽  
High Speed Flows

Abstract. We surveyed fast current sheet crossings (flapping motions) over the distance range 10–30 RE in the magnetotail covered by the Geotail spacecraft. Since the local tilts of these dynamic sheets are large and variable in these events, we compare three different methods of evaluating current sheet normals using 4-s/c Cluster data and define the success criteria for the single-spacecraft-based method (MVA) to obtain the reliable results. Then, after identifying more than ~1100 fast CS crossings over a 3-year period of Geotail observations in 1997–1999, we address their parameters, spatial distribution and activity dependence. We confirm that over the entire distance covered and LT bins, fast crossings have considerable tilts in the YZ plane (from estimated MVA normals) which show a preferential appearance of one (YZ kink-like) mode that is responsible for these severe current sheet perturbations. Their occurrence is highly inhomogeneous; it sharply increases with radial distance and has a peak in the tail center (with some duskward shift), resembling the occurrence of the BBFs, although there is no one-to-one local correspondence between these two phenomena. The crossing durations typically spread around 1 min and decrease significantly where the high-speed flows are registered. Based on an AE index superposed epoch study, the flapping motions prefer to appear during the substorm expansion phase, although a considerable number of events without any electrojet and auroral activity were also observed. We also present statistical distributions of other parameters and briefly discuss what could be possible mechanisms to generate the flapping motions.

scholarly journals Стенд для измерения крутящего момента маломощных энергоагрегатов

2020 ◽  
Author(s):  
A.I. Samsonov ◽  
A.N. Sobolenko
Keyword(s):  
Low Power ◽  
High Speed ◽  
Permanent Magnets ◽  
Eddy Currents ◽  
Small Scale ◽  
Torque Measurement ◽  
Brake Disk ◽  
Axis Of Rotation ◽  
Braking Force ◽  
The Magnetic Field

Предлагается тормоз с постоянными магнитами, при помощи которых можно исследовать маломощные высокоскоростные энергоагрегаты мощностью до 1 кВт. Принцип действия стенда основан на использовании силы торможения, вызванной вихревыми токами Фуко. Количество энергии, создаваемой токами Фуко и вызывающими силу торможения, прямо пропорционально квадрату частоты изменения магнитного поля. Нашем случае это частота вращения диска тормоза. Приведена принципиальная схема устройства стенда с магнитным тормозом у которых ось вращения не совпадала с осью вращения вала турбомашины. Проанализирован принцип его действия. Объяснен его недостаток. Предложена новая схема стенда, у которого ось вращения совпадает с осью вращения вала турбомашины. Показано, что в этом случае возможно точное количественное определение величины крутящего момента испытываемого энергоагрегата. Предложенный стенд для измерения крутящего момента рекомендуется использовать для крутящего момента при испытаниях микротурбин, маломощных двигателей беспилотных летательных аппаратов, триммеров и газонокосилок, электромоторов небольшой мощности.A brake with permanent magnets is proposed, with the help of which it is possible to study small-scale high-speed power units with a capacity of up to 1 kW. The principle of operation of the stand is based on the use of braking force caused by eddy currents Fouco. The amount of energy generated by Fouco currents and causing the braking force is directly proportional to the square of the frequency of the magnetic field. In our case, it is the speed of the brake disk. The schematic diagram of the device stand with a magnetic brake in which the axis of rotation does not coincide with the axis of rotation of the shaft of the turbomachine. The principle of its operation is analyzed. Explained by the lack of it. A new scheme of the stand, in which the axis of rotation coincides with the axis of rotation of the turbomachine shaft, is proposed. It is shown that in this case it is possible to accurately quantify the torque of the test power unit. The proposed stand for torque measurement is recommended for torque testing of microturbines, low-power engines of unmanned aerial vehicles, trimmers and lawn mowers, low-power electric motors.

scholarly journals Cluster magnetotail observations of a tailward-travelling plasmoid at substorm expansion phase onset and field aligned currents in the plasma sheet boundary layer

2005 ◽  
Vol 23 (12) ◽  
pp. 3667-3683 ◽  
Author(s):  
N. C. Draper ◽  
M. Lester ◽  
S. W. H. Cowley ◽  
J.A. Wild ◽  
S. E. Milan ◽  
...  
Keyword(s):  
Boundary Layer ◽  
Plasma Sheet ◽  
Neutral Line ◽  
Current System ◽  
Onset Time ◽  
Plasma Sheet Boundary Layer ◽  
Expansion Phase ◽  
Magnetometer Data ◽  
Reconnection Site ◽  
Substorm Onsets

Abstract. We present data from both ground- and space-based instruments for a substorm event which occurred on 5 October 2002, with an expansion phase onset time of 02:50 UT determined from the ground magnetometer data. During this substorm, the Cluster spacecraft were located around 15 RE downtail, 8 RE from midnight in the pre-midnight sector and just 2 RE above the equatorial plane (in GSM coordinates). At expansion phase onset the Cluster spacecraft were located in the plasma sheet, tailward of a near-Earth neutral line and detected a significant time delay of 6 min between the tail field Bz component becoming negative and the subsequent detection of Earthward flows. This is explained by the formation of a tailward-directed travelling compression region initially Earthward of the spacecraft; 7 min later the Cluster spacecraft entered the plasma sheet boundary layer; they remained in and close to the plasma sheet boundary layer for around 15 min before exiting to the lobe. The spacecraft then re-entered the plasma sheet 30 min after onset. Earthward then tailward directed currents detected in the plasma sheet boundary layer after onset indicate that the Cluster spacecraft encountered the dawnward and duskward portions of the reconnection flow associated current system with Region 1 sense, respectively. The reconnection site and current system were initially skewed towards the pre-midnight sector, consistent with previous observations that found the majority of substorm onsets located in this sector. At later times the reconnection site and current system had moved towards dawn, to be located more centrally in the midnight sector.

scholarly journals Studies of magnetotail dynamics and energy evolution during substorms using MHD simulations

2009 ◽  
Vol 27 (4) ◽  
pp. 1717-1727 ◽  
Author(s):  
S. Brogl ◽  
R. E. Lopez ◽  
M. Wiltberger ◽  
H. K. Rassoul
Keyword(s):  
Growth Phase ◽  
Plasma Sheet ◽  
Magnetic Energy ◽  
Substorm Onset ◽  
Energy Evolution ◽  
Polar Cap ◽  
Expansion Phase ◽  
Mhd Simulations ◽  
Hydrodynamic Code ◽  
Magnetotail Dynamics

Abstract. We examine the distribution and propagation of energy in the plasma sheet and lobes using observations and simulations for three substorms. The substorms occurred on 9 March 1995, 10 December 1996, and 27 August 2001 and have been simulated using the Lyon-Fedder-Mobarry magneto-hydrodynamic code. All three events occur over North America and show a clear substorm current wedge over the ground magnetometer chains of Alaska, Canada, and Greenland. The three simulations show the thinning of the plasma sheet during the growth phase of the event and an increase in the relative amount of thermal energy due to the compression of the plasma sheet. Generally, the total lobe energy, polar cap flux, and lobe magnetic field strength simultaneously increase during the growth phase, and polar cap flux and total lobe energy only start dropping at substorm onset, as measured by the CANOPUS magnetometer chain. Starting at time of onset and continuing throughout the expansion phase a transfer of magnetic energy from the lobes into the plasma sheet occurs, with the increase in the plasma sheet energy ranging from 30–40% of the energy that is released from the lobes.

scholarly journals Fully Automated Cultivation of Adipose-Derived Stem Cells in the StemCellDiscovery—A Robotic Laboratory for Small-Scale, High-Throughput Cell Production Including Deep Learning-Based Confluence Estimation

Processes ◽  
2021 ◽  
Vol 9 (4) ◽  
pp. 575
Author(s):  
Jelena Ochs ◽  
Ferdinand Biermann ◽  
Tobias Piotrowski ◽  
Frederik Erkens ◽  
Bastian Nießing ◽  
...  
Keyword(s):  
Stem Cells ◽  
Deep Learning ◽  
High Throughput ◽  
High Speed ◽  
New Technologies ◽  
Human Mesenchymal Stem Cells ◽  
Simulation Software ◽  
System Capacity ◽  
Small Scale ◽  
Production Environment

Laboratory automation is a key driver in biotechnology and an enabler for powerful new technologies and applications. In particular, in the field of personalized therapies, automation in research and production is a prerequisite for achieving cost efficiency and broad availability of tailored treatments. For this reason, we present the StemCellDiscovery, a fully automated robotic laboratory for the cultivation of human mesenchymal stem cells (hMSCs) in small scale and in parallel. While the system can handle different kinds of adherent cells, here, we focus on the cultivation of adipose-derived hMSCs. The StemCellDiscovery provides an in-line visual quality control for automated confluence estimation, which is realized by combining high-speed microscopy with deep learning-based image processing. We demonstrate the feasibility of the algorithm to detect hMSCs in culture at different densities and calculate confluences based on the resulting image. Furthermore, we show that the StemCellDiscovery is capable of expanding adipose-derived hMSCs in a fully automated manner using the confluence estimation algorithm. In order to estimate the system capacity under high-throughput conditions, we modeled the production environment in a simulation software. The simulations of the production process indicate that the robotic laboratory is capable of handling more than 95 cell culture plates per day.

Experimental investigation and optimization on field shaper structure parameters in magnetic pulse welding

2021 ◽  
pp. 095440542110148
Author(s):  
Yingzi Chen ◽  
Zhiyuan Yang ◽  
Wenxiong Peng ◽  
Huaiqing Zhang
Keyword(s):  
Magnetic Field ◽  
High Speed ◽  
Light Metal ◽  
Magnetic Pulse ◽  
Cross Sectional ◽  
Magnetic Pulse Welding ◽  
Pulse Welding ◽  
Sectional Shape ◽  
Welding System ◽  
The Magnetic Field

Magnetic pulse welding is a high-speed welding technology, which is suitable for welding light metal materials. In the magnetic pulse welding system, the field shaper can increase the service life of the coil and contribute to concentrating the magnetic field in the welding area. Therefore, optimizing the structure of the field shaper can effectively improve the efficiency of the system. This paper analyzed the influence of cross-sectional shape and inner angle of the field shaper on the ability of concentrating magnetic field via COMSOL software. The structural strength of various field shapers was also analyzed in ABAQUS. Simulation results show that the inner edge of the field shaper directly affects the deformation and welding effect of the tube. So, a new shape of field shaper was proposed and the experimental results prove that the new field shaper has better performance than the conventional field shaper.

scholarly journals 3–D Models of Galaxy Magnetic Fields with Spiral Shocks

1990 ◽  
Vol 140 ◽  
pp. 133-134
Author(s):  
J. Panesar ◽  
A.H. Nelson
Keyword(s):  
Gas Flow ◽  
Density Wave ◽  
Shock Velocity ◽  
Small Scale ◽  
Hydrodynamic Simulation ◽  
Dynamo Equation ◽  
Scale Turbulence ◽  
Wave Induced ◽  
The Magnetic Field ◽  
Stellar Density

We report here some preliminary results of 3–D numerical simulations of an α–ω dynamo in galaxies with differential rotation, small–scale turbulence, and a shock wave induced by a stellar density wave. We obtain the magnetic field from the standard dynamo equation, but include the spiral shock velocity field from a hydrodynamic simulation of the gas flow in a gravitational field with a spiral perturbation (Johns and Nelson, 1986).

scholarly journals Detonation effects of shallow buried explosive in sandy soil on target plate acceleration in a small-scale blast test

2018 ◽  
Vol 192 ◽  
pp. 02028
Author(s):  
Hassan Zulkifli Abu ◽  
Ibrahim Aniza ◽  
Mohamad Nor Norazman
Keyword(s):  
Sandy Soil ◽  
High Speed ◽  
Early Stage ◽  
Time History ◽  
Video Camera ◽  
Small Scale ◽  
Target Plate ◽  
Air Blast ◽  
High Speed Video Camera ◽  
The Impact

Small-scale blast tests were carried out to observe and measure the influence of sandy soil towards explosive blast intensity. The tests were to simulate blast impact imparted by anti-vehicular landmine to a lightweight armoured vehicle (LAV). Time of occurrence of the three phases of detonation phase in soil with respect to upward translation time of the test apparatus were recorded using high-speed video camera. At the same time the target plate acceleration was measured using shock accelerometer. It was observed that target plate deformation took place at early stage of the detonation phase before the apparatus moved vertically upwards. Previous data of acceleration-time history and velocity-time history from air blast detonation were compared. It was observed that effects of soil funnelling on blast wave together with the impact from soil ejecta may have contributed to higher blast intensity that characterized detonation in soil, where detonation in soil demonstrated higher plate velocity compared to what occurred in air blast detonation.

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