scholarly journals Heat flux effect in ηi-mode driven solitary and shock waves in electron-positron-ion plasma

2021 ◽  
Vol 49 (1) ◽  
Author(s):  
U. Zakir ◽  
◽  
K. Aziz ◽  
Q. Haque ◽  
A. Murad ◽  
...  
Keyword(s):  
Magnetic Field ◽  
Heat Flux ◽  
Density Ratio ◽  
Tokamak Plasma ◽  
Ion Temperature ◽  
Linear Dispersion ◽  
Ion Temperature Gradient ◽  
Ion Plasma ◽  
Electron Positron ◽  
Solitary And Shock Waves

The specific role of ion heat flux on the characteristics of the linear and nonlinear ion temperature gradient (ηi) driven mode in inhomogeneous electron-positron-ion plasma is presented. Inhomogeneity in density, temperature, and the magnetic field is considered. A modified linear dispersion relation is obtained, and its different limiting cases are when ηi 2/3, ωD(gradient in magnetic field) = 0 and β(density ratio of plasma species) = 1 are discussed. Furthermore, an expression for the anomalous transport coefficient of the present model is obtained. Nonlinear structure solutions in the form of solitons and shocks show that mode dynamics enhance in the presence of ion heat flux in electron-positron-ion plasma. The present study is essential in energy confinement devices such as tokamak because the heat flux observed experimentally in tokamak plasma is much higher than those described by collisions. Further, it could be helpful to understand the nonlinear electrostatic excitations in the interstellar medium.

Role of entropy in η i -mode driven nonlinear structures obtained by homotopy perturbation method in electron–positron–ion plasma

2021 ◽  
Vol 0 (0) ◽  
Author(s):  
Aziz Khan ◽  
U. Zakir ◽  
Qamar ul Haque ◽  
Anisa Qamar
Keyword(s):  
Perturbation Method ◽  
Low Frequency ◽  
Small Time ◽  
Tokamak Plasma ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Ion Plasma ◽  
Electron Positron ◽  
Solitary And Shock Waves ◽  
Strongly Agree

Abstract We present an analysis of the effect of entropy on ion temperature gradient η i -mode driven solitary and shock waves in electron–positron–ion plasma having density and temperature inhomogeneities. Linear and nonlinear analysis having solutions in form of solitons and shocks shows that entropy influence changes the drift mode instability. Different limiting cases when (i) temperature fluctuations due to E × B only (η i ≫ 2/3), (ii) in the absence of entropy and (iii) neglecting positron effect (β = 1) are discussed. The homotophy perturbation method (HPM) is applied on the derived Korteweg–de-Vries (KdV) and KdV–Burger equations under small time approximation. It is found that both results, those obtained analytically and by the HPM technique, strongly agree with each other. These investigations may be useful to study low frequency electrostatic modes in magnetized electron–positron–ion plasma. For illustration, the model has been applied to the nonlinear electrostatic excitations in interstellar medium and tokamak plasma.

On the effect of baryon loading in magnetized counterstreaming plasmas. I. Analytical investigation

2008 ◽  
Vol 74 (1) ◽  
pp. 79-90 ◽  
Author(s):  
R. C. TAUTZ ◽  
J.-I. SAKAI
Keyword(s):  
Magnetic Field ◽  
Growth Rates ◽  
Analytical Investigation ◽  
Linear Dispersion ◽  
Particle Species ◽  
Ion Plasma ◽  
Electron Positron ◽  
Background Magnetic Field ◽  
Unmagnetized Plasma ◽  
Homogeneous Background

AbstractAssuming a non-relativistic three species electron–positron–ion plasma, the counterstreaming instability is investigated for waves propagating parallel and perpendicular to a homogeneous background magnetic field. From the exact linear dispersion relations, it is shown analytically how the growth rates change with increasing baryon loading, revealing new characteristics that cannot be found either for an unmagnetized plasma involving three particle species or for a plasma with only two particle species.

scholarly journals Effects of Positron Density and Temperature on Large Amplitude Ion-acoustic Waves in an Electron - Positron - Ion Plasma

1997 ◽  
Vol 50 (2) ◽  
pp. 309 ◽  
Author(s):  
Y. N. Nejoh
Keyword(s):  
Acoustic Waves ◽  
Large Amplitude ◽  
Density Ratio ◽  
Present Theory ◽  
Electron Mass ◽  
Mass Ratio ◽  
Ion Acoustic Waves ◽  
Ion Plasma ◽  
Electron Positron ◽  
Ion Acoustic

The nonlinear wave structures of large amplitude ion-acoustic waves are studied in a plasma with positrons. We have presented the region of existence of the ion-acoustic waves by analysing the structure of the pseudopotential. The region of existence sensitively depends on the positron to electron density ratio, the ion to electron mass ratio and the positron to electron temperature ratio. It is shown that the maximum Mach number increases as the positron temperature increases and the region of existence of the ion-acoustic waves spreads as the positron temperature increases. The present theory is applicable to analyse large amplitude ion-acoustic waves associated with positrons which may occur in space plasmas.

scholarly journals Beltrami fields in a hot electron–positron–ion plasma

2012 ◽  
Vol 78 (3) ◽  
pp. 207-210 ◽  
Author(s):  
M. IQBAL ◽  
P. K. SHUKLA
Keyword(s):  
Magnetic Field ◽  
Plasma Flow ◽  
Strong Interaction ◽  
Field Configuration ◽  
Hot Electron ◽  
Magnetic Field Configuration ◽  
Beltrami Fields ◽  
Ion Plasma ◽  
Electron Positron ◽  
Laboratory Plasmas

AbstractA possibility of relaxation of relativistically hot electron and positron (e − p) plasma with a small fraction of hot or cold ions has been investigated analytically. It is observed that a strong interaction of plasma flow and field leads to a non-force-free relaxed magnetic field configuration governed by the triple curl Beltrami (TCB) equation. The triple curl Beltrami (TCB) field composed of three different Beltrami fields gives rise to three multiscale relaxed structures. The results may have the strong relevance to some astrophysical and laboratory plasmas.

scholarly journals Transition to subcritical turbulence in a tokamak plasma

2016 ◽  
Vol 82 (6) ◽  
Author(s):  
F. van Wyk ◽  
E. G. Highcock ◽  
A. A. Schekochihin ◽  
C. M. Roach ◽  
A. R. Field ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Initial Perturbation ◽  
Outer Core ◽  
Transition To Turbulence ◽  
Tokamak Plasma ◽  
Ion Temperature ◽  
Flow Shear ◽  
Ion Temperature Gradient ◽  
Stability Threshold ◽  
Accretion Flows

Tokamak turbulence, driven by the ion-temperature gradient and occurring in the presence of flow shear, is investigated by means of local, ion-scale, electrostatic gyrokinetic simulations (with both kinetic ions and electrons) of the conditions in the outer core of the Mega-Ampere Spherical Tokamak (MAST). A parameter scan in the local values of the ion-temperature gradient and flow shear is performed. It is demonstrated that the experimentally observed state is near the stability threshold and that this stability threshold is nonlinear: sheared turbulence is subcritical, i.e. the system is formally stable to small perturbations, but, given a large enough initial perturbation, it transitions to a turbulent state. A scenario for such a transition is proposed and supported by numerical results: close to threshold, the nonlinear saturated state and the associated anomalous heat transport are dominated by long-lived coherent structures, which drift across the domain, have finite amplitudes, but are not volume filling; as the system is taken away from the threshold into the more unstable regime, the number of these structures increases until they overlap and a more conventional chaotic state emerges. Whereas this appears to represent a new scenario for transition to turbulence in tokamak plasmas, it is reminiscent of the behaviour of other subcritically turbulent systems, e.g. pipe flows and Keplerian magnetorotational accretion flows.

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