Bounded anisotropy fluid model for ion temperature evolution applied to AMPTE/IRM magnetosheath data

1995 ◽  
Vol 100 (A8) ◽  
pp. 14925 ◽  
Author(s):  
Richard E. Denton ◽  
Xinlin Li ◽  
Tai-Duc Phan
Keyword(s):  
Fluid Model ◽  
Temperature Evolution ◽  
Ion Temperature

scholarly journals Ion temperature evolution in an ultracold neutral plasma

2015 ◽  
Vol 22 (3) ◽  
pp. 033513 ◽  
Author(s):  
P. McQuillen ◽  
T. Strickler ◽  
T. Langin ◽  
T. C. Killian
Keyword(s):  
Temperature Evolution ◽  
Ion Temperature ◽  
Neutral Plasma

scholarly journals Dependence on ion temperature of shallow-angle magnetic presheaths with adiabatic electrons

2019 ◽  
Vol 85 (6) ◽  
Author(s):  
Alessandro Geraldini ◽  
F. I. Parra ◽  
F. Militello
Keyword(s):  
Magnetic Field ◽  
Fluid Model ◽  
Boltzmann Distribution ◽  
Distribution Functions ◽  
Magnetized Plasma ◽  
Electron Mass ◽  
Ion Temperature ◽  
Ion Distribution ◽  
Ionic Charge ◽  
The Magnetic Field

The magnetic presheath is a boundary layer occurring when magnetized plasma is in contact with a wall and the angle $\unicode[STIX]{x1D6FC}$ between the wall and the magnetic field $\boldsymbol{B}$ is oblique. Here, we consider the fusion-relevant case of a shallow-angle, $\unicode[STIX]{x1D6FC}\ll 1$ , electron-repelling sheath, with the electron density given by a Boltzmann distribution, valid for $\unicode[STIX]{x1D6FC}/\sqrt{\unicode[STIX]{x1D70F}+1}\gg \sqrt{m_{\text{e}}/m_{\text{i}}}$ , where $m_{\text{e}}$ is the electron mass, $m_{\text{i}}$ is the ion mass, $\unicode[STIX]{x1D70F}=T_{\text{i}}/ZT_{\text{e}}$ , $T_{\text{e}}$ is the electron temperature, $T_{\text{i}}$ is the ion temperature and $Z$ is the ionic charge state. The thickness of the magnetic presheath is of the order of a few ion sound Larmor radii $\unicode[STIX]{x1D70C}_{\text{s}}=\sqrt{m_{\text{i}}(ZT_{\text{e}}+T_{\text{i}})}/ZeB$ , where e is the proton charge and $B=|\boldsymbol{B}|$ is the magnitude of the magnetic field. We study the dependence on $\unicode[STIX]{x1D70F}$ of the electrostatic potential and ion distribution function in the magnetic presheath by using a set of prescribed ion distribution functions at the magnetic presheath entrance, parameterized by $\unicode[STIX]{x1D70F}$ . The kinetic model is shown to be asymptotically equivalent to Chodura’s fluid model at small ion temperature, $\unicode[STIX]{x1D70F}\ll 1$ , for $|\text{ln}\,\unicode[STIX]{x1D6FC}|>3|\text{ln}\,\unicode[STIX]{x1D70F}|\gg 1$ . In this limit, despite the fact that fluid equations give a reasonable approximation to the potential, ion gyro-orbits acquire a spatial extent that occupies a large portion of the magnetic presheath. At large ion temperature, $\unicode[STIX]{x1D70F}\gg 1$ , relevant because $T_{\text{i}}$ is measured to be a few times larger than $T_{\text{e}}$ near divertor targets of fusion devices, ions reach the Debye sheath entrance (and subsequently the wall) at a shallow angle whose size is given by $\sqrt{\unicode[STIX]{x1D6FC}}$ or $1/\sqrt{\unicode[STIX]{x1D70F}}$ , depending on which is largest.

Study of mirror effect on scrape-off layer-divertor plasma based on a generalized fluid model incorporating ion temperature anisotropy

2018 ◽  
Vol 58 (6-8) ◽  
pp. 556-562 ◽  
Author(s):  
S. Togo ◽  
T. Takizuka ◽  
D. Reiser ◽  
K. Hoshino ◽  
K. Ibano ◽  
...  
Keyword(s):  
Fluid Model ◽  
Mirror Effect ◽  
Ion Temperature ◽  
Temperature Anisotropy

The Boltzmann relation in electronegative plasmas: When is it permissible to use it?

2000 ◽  
Vol 64 (2) ◽  
pp. 131-153 ◽  
Author(s):  
R. N. FRANKLIN ◽  
J. SNELL
Keyword(s):  
Fluid Model ◽  
Negative Ions ◽  
Ionization Rate ◽  
Negative Ion ◽  
Simple Relationship ◽  
Ion Temperature ◽  
Ion Density ◽  
Positive Ions ◽  
Electronegative Plasmas ◽  
Low Pressures

This paper reports the results of computations to obtain the spatial distributions of the charged particles in a bounded active plasma dominated by negative ions. Using the fluid model with a constant collision frequency for electrons, positive ions and negative ions the cases of both detachment-dominated gases (such as oxygen) and recombination-dominated gases (such as chlorine) are examined. It is concluded that it is valid to use a Boltzmann relation ne = ne0exp(eV/kT) for the electrons of density ne, where the temperature T is approximately the electron temperature Te, and that the density nn of the negative ions at low pressures obeys nn = nn0exp(eV/kTn), where Tn is the negative-ion temperature. However, at high pressure in detachment-dominated gases where the ratio of negative-ion density to electron density is constant and greater than unity, and when the attachment rate is larger than the ionization rate, the negative ions are distributed with the same effective temperature as the electrons. In all other cases there is no simple relationship. Thus to put nn/ne = const, nn = ne0exp(eV/kTe) and nn = nn0exp(eV/kTn) simultaneously is mathematically inconsistent and physically unsound. Accordingly, expressions deduced for ambipolar diffusion coefficients based on these assumptions have no validity. The correct expressions for the situation where nn/ne = const are obtained without invoking a Boltzmann relation for the negative ions.

Joining sheath to plasma in electronegative gases at low pressures using matched asymptotic approximations

1999 ◽  
Vol 62 (5) ◽  
pp. 541-559 ◽  
Author(s):  
M. S. BENILOV ◽  
R. N. FRANKLIN
Keyword(s):  
Fluid Model ◽  
Complex Structure ◽  
Density Ratio ◽  
Debye Length ◽  
Plasma Sheath ◽  
Negative Ion ◽  
Ion Temperature ◽  
Ion Motion ◽  
High Concentrations ◽  
Low Pressures

The method of matched asymptotic expansions is used to examine the structure of the plasma sheath of the positive column at low pressure in electronegative gases using the fluid model to describe the positive-ion motion. It is shown that at low negative-ion concentrations, and at high concentrations, the structure is that of a plasma joined to a thin sheath, but that for the electron/negative-ion temperature ratio Te/Tn ≡ ε > 5 + √24, and for a well-defined range of A ≡ nn0/ne0 (the central negative ion to electron density ratio) and for small Debye length, there is a more complex structure with a central negative-ion-dominated plasma surrounded by a quasiplasma in which density oscillations may occur before joining to a sheath. This is in agreement with recent computations using the same model.

scholarly journals The ion temperature evolution on TCA during Alfven wave heating and in non-stationary Ohmic conditions

1989 ◽  
Vol 31 (4) ◽  
pp. 527-547 ◽  
Author(s):  
A de Chambrier ◽  
B P Duval ◽  
J B Lister ◽  
F J Mompean ◽  
J -M Moret
Keyword(s):  
Temperature Evolution ◽  
Alfven Wave ◽  
Ion Temperature ◽  
Wave Heating

scholarly journals Zonally dominated dynamics and Dimits threshold in curvature-driven ITG turbulence

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
Plamen G. Ivanov ◽  
A. A. Schekochihin ◽  
W. Dorland ◽  
A. R. Field ◽  
F. I. Parra
Keyword(s):  
Temperature Gradient ◽  
Numerical Simulations ◽  
Blow Up ◽  
Fluid Model ◽  
Equilibrium Temperature ◽  
Plasma Phys ◽  
Turbulent Heat ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Saturated State

The saturated state of turbulence driven by the ion-temperature-gradient instability is investigated using a two-dimensional long-wavelength fluid model that describes the perturbed electrostatic potential and perturbed ion temperature in a magnetic field with constant curvature (a $Z$ -pinch) and an equilibrium temperature gradient. Numerical simulations reveal a well-defined transition between a finite-amplitude saturated state dominated by strong zonal-flow and zonal temperature perturbations, and a blow-up state that fails to saturate on a box-independent scale. We argue that this transition is equivalent to the Dimits transition from a low-transport to a high-transport state seen in gyrokinetic numerical simulations (Dimits et al., Phys. Plasmas, vol. 7, 2000, 969). A quasi-static staircase-like structure of the temperature gradient intertwined with zonal flows, which have patch-wise constant shear, emerges near the Dimits threshold. The turbulent heat flux in the low-collisionality near-marginal state is dominated by turbulent bursts, triggered by coherent long-lived structures closely resembling those found in gyrokinetic simulations with imposed equilibrium flow shear (van Wyk et al., J. Plasma Phys., vol. 82, 2016, 905820609). The breakup of the low-transport Dimits regime is linked to a competition between the two different sources of poloidal momentum in the system – the Reynolds stress and the advection of the diamagnetic flow by the $\boldsymbol {E}\times \boldsymbol {B}$ flow. By analysing the linear ion-temperature-gradient modes, we obtain a semi-analytic model for the Dimits threshold at large collisionality.

scholarly journals Analysis of Ion-Temperature-Gradient Instabilities Using a Gyro-Fluid Model in Cylindrical Plasmas

2015 ◽  
Vol 10 (0) ◽  
pp. 3401060-3401060 ◽  
Author(s):  
Genryu HATTORI ◽  
Naohiro KASUYA ◽  
Masatoshi YAGI
Keyword(s):  
Temperature Gradient ◽  
Fluid Model ◽  
Ion Temperature ◽  
Ion Temperature Gradient

Influence of ion temperature on plasma sheath transition

2009 ◽  
Vol 76 (2) ◽  
pp. 247-255 ◽  
Author(s):  
HAMID GHOMI ◽  
MANSOUR KHORAMABADI
Keyword(s):  
Lower Limit ◽  
Fluid Model ◽  
Elastic Collision ◽  
Plasma Sheath ◽  
Ion Temperature ◽  
Transition Velocity ◽  
Two Fluid Model ◽  
Lower Limits ◽  
Two Fluid

AbstractUsing a two-fluid model, the ion transition from plasma sheath boundary is investigated taking into account the effect of the finite ion temperature. It is shown that by considering the effects of neutral-ion elastic collision on the sheath, there will be an upper as well as a lower limit for the ion transition velocity into the sheath. The dependency of upper and lower limits of the ion transition velocity on the ion temperature is investigated, and it is shown that the finite ion temperature only affects lower limits in non-hot plasmas.

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