scholarly journals Breakdown Phase in the GOLEM Tokamak and Its Impact on Plasma Performance

2021 ◽  
Vol 66 (3) ◽  
pp. 231
Author(s):  
Y. Siusko ◽  
V. Svoboda ◽  
J. Stockel ◽  
I. Garkusha ◽  
D. Solyakov ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Time Delay ◽  
Electric Field ◽  
Undergraduate Students ◽  
Temporal Delay ◽  
Plasma Parameters ◽  
Dominant Mechanism ◽  
Breakdown Time ◽  
National University ◽  
The Mean

The effect of the breakdown phase on subsequent plasma parameters in GOLEM tokamak is investigated remotely. The dependence of the breakdown voltage and the breakdown time on the time delay between the switchings-on of a toroidal magnetic field Bt and a toroidal electric field Et for different groups of the pressure magnitudes is built. The performed experiments have shown that, for GOLEM tokamak, the shorter the temporal delay, the better are the mean plasma parameters. In addition, the breakdown phase is discussed in more details. In the discussion, the avalanche phase of the breakdown is analyzed. The dominant mechanism of particle losses during the avalanche phase, future steps, and tasks are discussed and set. The experiments on studying the breakdown phase have been carried out remotely on GOLEM tokamak by undergraduate students of V.N. Karazin Kharkiv National University.

scholarly journals A case study of the plasma in the magneto-sheath using the numerical magnetosheath-magnetosphere model and THEMIS measure-ments

2018 ◽  
Vol 145 ◽  
pp. 03004
Author(s):  
Polya Dobreva ◽  
Olga Nitcheva ◽  
Monio Kartalev
Keyword(s):  
Magnetic Field ◽  
Field Model ◽  
Specific Aspect ◽  
Plasma Parameters ◽  
Ion Density ◽  
Magnetic Field Model ◽  
Wind Spacecraft ◽  
The Mean ◽  
The Magnetic Field

This paper presents a case study of the plasma parameters in the magnetosheath, based on THEMIS measurements. As a theoretical tool we apply the self-consistent magnetosheath-magnetosphere model. A specific aspect of the model is that the positions of the bow shock and the magnetopause are self-consistently determined. In the magnetosheath the distribution of the velocity, density and temperature is calculated, based on the gas-dynamic theory. The magnetosphere module allows for the calculation of the magnetopause currents, confining the magnetic field into an arbitrary non-axisymmetric magnetopause. The variant of the Tsyganenko magnetic field model is applied as an internal magnetic field model. As solar wind monitor we use measurements from the WIND spacecraft. The results show that the model quite well reproduces the values of the ion density and velocity in the magnetosheath. The simlicity of the model allows calulations to be perforemed on a personal computer, which is one of the mean advantages of our model.

scholarly journals Investigation on High Velocity Plasmas and Field Aligned Currents at High Latitudes

2020 ◽  
pp. 22-29
Author(s):  
J. C. K. Akhila ◽  
C. P. Anil Kumar
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
High Velocity ◽  
Transmission Function ◽  
External Loading ◽  
Plasma Parameters ◽  
Spherical Cap ◽  
Field Aligned Current ◽  
Field Lines ◽  
Spherical Cap Harmonic Analysis

The interaction of high velocity plasma with Earth’s magnetic field is fundamental and offer many questions on high latitude electrodynamics. The problems associated with influence of electric field and Field Aligned Current (FAC) generation is investigated with the aid of spherical cap harmonic analysis at 830 Mag. Lat. in southern hemispheres. The investigation is done on the cases with different Interplanetary Magnetic Field (IMF) conditions after the earth directed solar events. The helio-plasma parameters viz., density, velocity, energy, electron temperature are also noted during the field aligned current studies. It seems that, due to external magnetic field influence polarization of plasma electric field take place (reorientation of the convective cells). It happens with different orientation as per the magnitude and direction of By and Bz component and the horizontal currents. It is noted that the FAC value also depends on kinetic energy of the plasma streams and conductivity of external loading. As the plasma decelerates by force Jsw X Esw, the resultant current may extend along the field lines. Increases in the FAC density are seemed to be proportional to the transmission function.

Drift instability in the presence of a parallel electric field and an inhomogeneous magnetic field: particle aspect analysis

1991 ◽  
Vol 46 (1) ◽  
pp. 49-62 ◽  
Author(s):  
M. S. Tiwari ◽  
P. Varma
Keyword(s):  
Magnetic Field ◽  
Growth Rate ◽  
Electric Field ◽  
Inhomogeneous Magnetic Field ◽  
Thermal Velocity ◽  
Parallel Electric Field ◽  
Zeroth Order ◽  
Plasma Parameters ◽  
Drift Instability ◽  
Particle Aspect Analysis

The theory of particle aspect analysis is extended to a drift wave in the presence of an inhomogeneous magnetic field and an applied electric field parallel to the ambient magnetic field. The effect of a parallel electric field is included in the zeroth-order distribution function through modification of the particle thermal velocity in that direction. The plasma under consideration is assumed to be anisotropic and with low β. The dispersion relation and growth rate are evaluated and discussed for particular plasma parameters. The limitations of the theory are also pointed out.

The theory of the cosmic background radio signal received within the ionosphere

1964 ◽  
Vol 277 (1370) ◽  
pp. 365-384 ◽  
Keyword(s):  
Magnetic Field ◽  
Refractive Index ◽  
Magnetic Fields ◽  
Electric Field ◽  
Free Space ◽  
Wave Theory ◽  
Ordinary Wave ◽  
Mean Square ◽  
Ray Theory ◽  
The Mean

The electric and magnetic fields to be expected within the ionosphere from a background source uniformly distributed across the sky are studied. The ray theory for an isotropic, horizontally stratified loss-free slowly varying ionosphere is first given, and it is shown that the mean-square moduli of the electric field components have n times their free-space value, and the mean-square moduli of the magnetic field components have n 3 times their free-space value where n is the local refractive index. The corrections to be expected when a full-wave theory is used are discussed. The ray theory for an anisotropic, loss-free ionosphere is then given and it is shown that the energy flux in a given direction is proportional to the Gaussian curvature at the associated point on the refractive index surface. For the ordinary wave, near the level of reflexion, the electric field is predominantly parallel to the earth’s magnetic field, and the small perpendicular component is nearly 100% circularly polarized. Results for the magnetic fields and for the fields of the extraordinary wave are also given and discussed.

scholarly journals Dental Anxiety among Undergraduate Students of a National University in Brunei Darussalam

2021 ◽  
Vol 4 (1) ◽  
Author(s):  
Zhi Qi Tan ◽  
Ishak Nurul Sa'idah ◽  
Hanif Abdul Rahman ◽  
Jagjit Singh Dhaliwal
Keyword(s):  
Undergraduate Students ◽  
Treatment Plan ◽  
Dental Anxiety ◽  
Population Group ◽  
Cross Sectional ◽  
Dental Visits ◽  
Brunei Darussalam ◽  
Significant Difference ◽  
National University ◽  
The Mean

This study aimed to investigate the nature of dental anxiety among undergraduate students of a national university in Brunei Darussalam. Participants were undergraduate students from different faculties of a national university. It was a cross-sectional study using a questionnaire that included their personal demographics, the Modified Dental Anxiety Scale (MDAS) questions and questions regarding their last dental visit. The degree of anxiety was compared in relation to different factors as mentioned above. Data collected was analyzed using independent t-test and one-way ANOVA. Results showed that the frequency of dental anxiety among the undergraduate students was 70.8%. The mean total MDAS score was 12.3 ± 4.28. Females (13.5±5.12) were more dentally anxious than males (12.2±4.73) (p=0.027). There was a significant difference in the mean MDAS score (p < 0.001) when comparing patterns of dental visits with dental anxiety. More students were fearful of local anesthetic injection than getting tooth drilled. (4) Conclusion: Dental anxiety still remains as one of the obstacles that clinicians face. More studies need to be done to provide a better understanding on how dental anxiety can affect the pattern of dental visits. Future studies should explore the etiology of dental anxiety. This study helps to create awareness on the presence of dental anxiety amongst the existent population group and also to aid clinicians in identifying areas of dentistry where patients are most anxious about in order to come up with a suitable treatment plan.

A confident source of hard X-rays: radiation from a tokamak applicable for runaway electrons diagnosis

2016 ◽  
Vol 23 (5) ◽  
pp. 1227-1231 ◽  
Author(s):  
M. Kafi ◽  
A. Salar Elahi ◽  
M. Ghoranneviss ◽  
M. R. Ghanbari ◽  
M. K. Salem
Keyword(s):  
Magnetic Field ◽  
Electric Field ◽  
High Energy ◽  
Toroidal Magnetic Field ◽  
Vacuum Vessel ◽  
X Rays ◽  
Runaway Electrons ◽  
High Energy Electrons ◽  
High Loop ◽  
The Mean

In a tokamak with a toroidal electric field, electrons that exceed the critical velocity are freely accelerated and can reach very high energies. These so-called `runaway electrons' can cause severe damage to the vacuum vessel and are a dangerous source of hard X-rays. Here the effect of toroidal electric and magnetic field changes on the characteristics of runaway electrons is reported. A possible technique for runaways diagnosis is the detection of hard X-ray radiation; for this purpose, a scintillator (NaI) was used. Because of the high loop voltage at the beginning of a plasma, this investigation was carried out on toroidal electric field changes in the first 5 ms interval from the beginning of the plasma. In addition, the toroidal magnetic field was monitored for the whole discharge time. The results indicate that with increasing toroidal electric field the mean energy of runaway electrons rises, and also an increase in the toroidal magnetic field can result in a decrease in intensity of magnetohydrodynamic oscillations which means that for both conditions more of these high-energy electrons will be generated.

The Long‐Term Evolution of AR 7978: The Scalings of the Coronal Plasma Parameters with the Mean Photospheric Magnetic Field

2003 ◽  
Vol 586 (1) ◽  
pp. 579-591 ◽  
Author(s):  
L. van Driel‐Gesztelyi ◽  
P. Demoulin ◽  
C. H. Mandrini ◽  
L. Harra ◽  
J. A. Klimchuk
Keyword(s):  
Magnetic Field ◽  
Long Term Evolution ◽  
Photospheric Magnetic Field ◽  
Coronal Plasma ◽  
Plasma Parameters ◽  
Term Evolution ◽  
The Mean

scholarly journals Gravitational lensing by a magnetized compact object in the presence of plasma

2019 ◽  
Vol 28 (16) ◽  
pp. 2040013 ◽  
Author(s):  
Bobur Turimov ◽  
Bobomurat Ahmedov ◽  
Ahmadjon Abdujabbarov ◽  
Cosimo Bambi
Keyword(s):  
Magnetic Field ◽  
Time Delay ◽  
Gravitational Lensing ◽  
Zeeman Effect ◽  
Compact Object ◽  
Field Approximation ◽  
Weak Field ◽  
Magnetized Plasma ◽  
Electromagnetic Signal ◽  
Plasma Parameters

In the weak field approximation, we study the gravitational lensing by spherical symmetric compact object immersed in magnetic field in the presence of magnetized plasma. The external magnetic field causes the split of the deflection angle of the photon, Einstein ring and Einstein cross as the counterpart of the Zeeman effect. In particular, the magnetic field affects the magnification of images, creating additional components. We also study the time delay of an electromagnetic signal due to the geometry and the gravitational field around the lensing source. We show that the time delay of the electromagnetic signal strongly depends on the plasma parameters, and it slightly decreases in the plasma in comparison with that in vacuum.

scholarly journals On nonlinear Alfvén-cyclotron waves in multi-species plasma

2010 ◽  
Vol 77 (3) ◽  
pp. 385-403 ◽  
Author(s):  
ECKART MARSCH ◽  
DANIEL VERSCHAREN
Keyword(s):  
Magnetic Field ◽  
Kinetic Energy ◽  
Electric Field ◽  
Transverse Magnetic Field ◽  
Acoustic Waves ◽  
Mean Field ◽  
Transverse Magnetic ◽  
Longitudinal Electric Field ◽  
Mhd Turbulence ◽  
The Mean

AbstractLarge-amplitude Alfvén waves are ubiquitous in space plasmas and a main component of magnetohydrodynamic (MHD) turbulence in the heliosphere. As pump waves, they are prone to parametric instability by which they can generate cyclotron and acoustic daughter waves. Here, we revisit a related process within the framework of the multi-fluid equations for a plasma consisting of many species. The nonlinear coupling of the Alfvén wave to acoustic waves is studied, and a set of compressive and coupled-wave equations for the transverse magnetic field and longitudinal electric field is derived for waves propagating along the mean-field direction. It turns out that slightly compressive Alfvén waves exert, through induced gyro-radius and kinetic-energy modulations, an electromotive force on the particles in association with a longitudinal electric field, which has a potential that is given by the gradient of the transverse kinetic energy of the particles gyrating about the mean field. This in turn drives electric fluctuations (sound and ion-acoustic waves) along the mean magnetic field, which can nonlinearly react back on the transverse magnetic field. Mutually coupled Alfvén-cyclotron--acoustic waves are thus excited, a nonlinear process that can drive a cascade of wave energy in the plasma, and may generate compressive microturbulence. These driven electric fluctuations might have consequences for the dissipation of an MHD turbulence and, thus, for the heating and acceleration of particles in the solar wind.

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