scholarly journals Tungsten and Molybdenum Surfaces Exposed to Warm Deuterium Ion Plasma with Q-Nonextensive Distribution of Electrons

2020 ◽  
Vol 6 (1) ◽  
pp. 50-58
Author(s):  
S. Basnet ◽  
R. Khanal
Keyword(s):  
Magnetic Field ◽  
Impact Energy ◽  
Target Surface ◽  
Plasma Sheath ◽  
Magnetized Plasma ◽  
Sheath Region ◽  
Two Fluids ◽  
Positive Ions ◽  
Nonextensive Distribution ◽  
The Impact

 This work is concerned with the effect of non-Maxwellian electrons and obliqueness of magnetic field on magnetized plasma sheath characteristics, in which plasma interacts with tungsten (W) and molybdenum (Mo) surfaces via non-neutral plasma sheath using two fluids model. It is assumed that the singly charged positive ions are treated as warm fluid whereas the electrons obey q-nonextensive distribution. It is found that the q-nonextensive distributed electrons and the temperature of ions affect the entrance velocity of positive ions, which is a key parameter in the plasma sheath formation. Also, the nonextensive parameter q affects the distribution of ions and electrons in the sheath region and their distributions explicitly related with the electrostatic potential variation. The parallel and perpendicular components of ions velocity are affected by the obliqueness of magnetic field. As the nonextensivity of electrons increases, the gradient in electric potential increases towards the wall and hence the impact energy also increases. The obliqueness of magnetic field and impact energy of ions is a key factor that determines the physical sputtering rate, particle reflection and absorption from the target surface. Furthermore, the probability of particle reflection coefficient from the W-surface is higher than that of Mo-surface.

scholarly journals Temporal Ion Velocity Variation with Obliqueness in Magnetized Plasma Sheath

2021 ◽  
Vol 7 (2) ◽  
pp. 138-143
Author(s):  
B. R. Adhikari ◽  
R. Khanal
Keyword(s):  
Magnetic Field ◽  
Plasma Sheath ◽  
Magnetized Plasma ◽  
Velocity Variation ◽  
Physical Parameters ◽  
Sheath Region ◽  
Narrow Region ◽  
Force Equation ◽  
Ion Velocity ◽  
External Oblique Magnetic Field

A narrow region having sharp gradients in physical parameters is formed whenever plasma comes into contact with a material wall. In this work, the temporal velocity variation of ions in such a sheath has been studied in the presence of an external oblique magnetic field. The Lorentz force equation has been solved for the given boundary conditions using Runge-Kutta method. In order to satisfy the Bohm criterion, ions enter the sheath region with ion acoustic velocity. It is observed that all components of the velocity waves are damped in plasma in the time scale of one second. The computed oscillatory part of ion velocity match with the equation of the damped harmonic oscillator. Thus obtained damping constants as well as the frequency of all three components are nearly equal for obliqueness less than 600 after which they are distinctly different. This is due to the fact that the magnetic field becomes almost parallel to the wall. In earlier studies, only the final velocity profiles are reported and hence this study is useful in understanding how the ion velocities evolve in time as they move from sheath entrance towards the wall.

Effect of non-uniform magnetic field on two ion species plasma-wall transition

2021 ◽  
Author(s):  
Atit Deuja ◽  
Suresh Basnet ◽  
Raju Khanal
Keyword(s):  
Magnetic Field ◽  
Transition Region ◽  
Uniform Magnetic Field ◽  
Boltzmann Distribution ◽  
Magnetized Plasma ◽  
Magnetic Flux Density ◽  
Sheath Region ◽  
Average Value ◽  
Ion Species ◽  
The Magnetic Field

Abstract Fluid theory has been employed to investigate the magnetized plasma-wall transition properties for two ion species plasmas with a uniform background of neutral gas density in the presence of an external magnetic field. The external applied magnetic field is parallel to the surface and its magnitude varies in the direction perpendicular to the surface. The governing equations of ion and electron fluids include ionization and collision with neutral atoms. A comparative study of transition parameters for non-uniform and uniform magnetic fields is performed at equal values of the magnetic flux density at $x = 0$. This study shows that the sheath region shrinks for the non-uniform magnetic field case, essentially in reason of the lower value of the average magnetic field intensity in the plasma-wall transition region. We introduce a figure of merit to quantify the non-uniformity of the magnetic field $(B_{\mathrm{max}}-B_{\mathrm{min}})/B_{\mathrm{max}}$, and show that for its value 0.21 it is possible to model the plasma-wall transition region considering the magnetic field as uniform and equal to its average value. Furthermore, we find that the density distribution of electrons close to the surface deviates from the Boltzmann distribution due to the influence of a strong magnetic field.

scholarly journals BEAT FREQUENCY AND VELOCITY VARIATION OF IONS IN A MAGNETIZED PLASMA SHEATH FOR DIFFERENT OBLIQUENESS OF THE MAGNETIC FIELD

2019 ◽  
Vol 23 (1) ◽  
pp. 88-92
Author(s):  
B. R. Adhikari ◽  
S. Basnet ◽  
H. P. Lamichhane ◽  
R. Khanal
Keyword(s):  
Magnetic Field ◽  
Beat Frequency ◽  
Maximum Amplitude ◽  
Mean Value ◽  
Plasma Sheath ◽  
Magnetized Plasma ◽  
Velocity Variation ◽  
Constant Frequency ◽  
Mean Values ◽  
The Mean

 Beat frequency and velocity variation of ions in a magnetized plasma sheath has been numerically investigated by using a kinetic trajectory simulation (KTS) model for varying obliqueness of the external magnetic field in presence of an electric field. Angular dependence of mean value, maximum amplitude, damping constant, frequency of oscillation and beat frequency have been studied. As the obliqueness of the field changes the mean values, beat frequency as well as the maximum amplitude of the velocity components also change but frequency of oscillation remains almost the same.

The Impact of Normal Magnetic Fields on Instability of Thermocapillary Convection in a Two-Layer Fluid System

2009 ◽  
Vol 131 (6) ◽  
Author(s):  
Hulin Huang ◽  
Xiaoming Zhou
Keyword(s):  
Magnetic Field ◽  
Field Strength ◽  
Magnetic Field Strength ◽  
Thermocapillary Convection ◽  
Film Coating ◽  
Surface Tension Gradient ◽  
Fluid System ◽  
Two Fluids ◽  
The Impact ◽  
The Magnetic Field

When a temperature gradient is imposed along a liquid-liquid interface, thermocapillary convection is driven by the surface tension gradient. Such flow occurs in many application processes, such as thin-film coating, metal casting, and crystal growth. In this paper, the effect of a normal magnetic field, which is perpendicular to the interface, on the instability of thermocapillary convection in a rectangular cavity with differentially heated sidewalls, filled with two viscous, immiscible, incompressible fluids, is studied under the absence of gravity. In the two-layer fluid system, the upper layer fluid is electrically nonconducting encapsulant B2O3, while the underlayer fluid is electrically conducting molten InP. The interface between the two fluids is assumed to be flat and nondeformable. The results show that the two-layer fluid system still experiences a wavelike state when the magnetic field strength Bz is less than 0.04 T. The wave period increases and the amplitude decreases with the increasing of magnetic field strength. However, the convective flow pattern becomes complicated with a variable period, while the perturbation begins to fall into oblivion as the magnetic field intensity is larger than 0.05 T. When Bz=0.1 T, the wavelike state does not occur, the thermocapillary convection instability is fully suppressed, and the unsteady convection is changed to a steady thermocapillary flow.

Predicting geo-effectiveness of CMEs with EUHFORIA coupled to OpenGGCM

2021 ◽  
Author(s):  
Anwesha Maharana ◽  
Camilla Scolini ◽  
Joachim Raeder ◽  
Stefaan Poedts
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Weather Forecasting ◽  
Flux Rope ◽  
Solar Wind Plasma ◽  
Geomagnetic Disturbance ◽  
Propagation Model ◽  
Magnetized Plasma ◽  
Future Work ◽  
The Impact

<div> <p>The <strong>EU</strong>ropean <strong>H</strong>eliospheric <strong>FOR</strong>ecasting <strong>I</strong>nformation <strong>A</strong>sset (<strong>EUHFORIA</strong>, Pomoell and Poedts, 2018) is a physics-based heliospheric and CME propagation model designed for space weather forecasting. Although EUHFORIA can predict the solar wind plasma and magnetic field parameters at Earth, it is not designed to evaluate indices like Disturbance-storm-time (Dst) or Auroral Electrojet (AE) that quantify the impact of the magnetized plasma encounters on Earth’s magnetosphere. To overcome this limitation, we coupled EUHFORIA with <strong>Open</strong> <strong>G</strong>eospace <strong>G</strong>eneral <strong>C</strong>irculation <strong>M</strong>odel (<strong>OpenGGCM</strong>, Raeder et al, 1996) which is a magnetohydrodynamic model of Earth’s magnetosphere. In this coupling, OpenGGCM takes the solar wind and interplanetary magnetic field obtained from EUHFORIA simulation as input to produce the magnetospheric and ionospheric parameters of Earth. We perform test runs to validate the coupling with real CME events modelled using flux rope models like Spheromak and FRi3D. We compare these simulation results with the indices obtained from OpenGGCM simulations driven by the measured solar wind data from spacecrafts like WIND. We further discuss how the choice of CME model and observationally constrained parameters influences the input parameters, and hence the geomagnetic disturbance indices estimated by OpenGGCM. We highlight limitations of the coupling and suggest improvements for future work. </p> </div>

scholarly journals Variation of velocity component of ions in a magnetized plasma sheath for different obliqueness of the magnetic field

2019 ◽  
Vol 8 ◽  
pp. 71-78
Author(s):  
Bhesha Raj Adhikari ◽  
Suresh Basnet ◽  
Hari Prasad Lamichhane ◽  
Raju Khanal
Keyword(s):  
Magnetic Field ◽  
Velocity Component ◽  
Full Text ◽  
Plasma Sheath ◽  
Magnetized Plasma ◽  
The Magnetic Field

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