# Turbulent momentum transport due to neoclassical flows

Intrinsic toroidal rotation in a tokamak can be driven by turbulent momentum transport due to neoclassical flow effects breaking a symmetry of turbulence. In this paper we categorize the contributions due to neoclassical effects to the turbulent momentum transport, and evaluate each contribution using gyrokinetic simulations. We find that the relative importance of each contribution changes with collisionality. For low collisionality, the dominant contributions come from neoclassical particle and parallel flows. For moderate collisionality, there are non- negligible contributions due to neoclassical poloidal electric field and poloidal gradients of density and temperature, which are not important for low collisionality.

**Comments:**28 pages, 5 figures, and 7 tables

## Similar Publications

Very strong magnetic fields can arise in non-central heavy-ion collisions at ultrarelativistic energies, which may not decay quickly in a conducting plasma. We carry out relativistic magnetohydrodynamics (RMHD) simulations to study the effects of this magnetic field on the evolution of the plasma and on resulting flow fluctuations in the ideal RMHD limit. Our results show that magnetic field leads to enhancement in elliptic flow, though in general effects of magnetic field on elliptic flow are very complex. Read More

**Affiliations:**

^{1}Max-Planck-Institut für Plasmaphysik,

^{2}Department of Physics, Chalmers University of Technology,

^{3}Max-Planck-Institut für Plasmaphysik,

^{4}Max-Planck-Institut für Plasmaphysik

**Category:**Physics - Plasma Physics

A potential threat to the performance of magnetically confined fusion plasmas is the problem of impurity accumulation, which causes the concentration of highly charged impurity ions to rise uncontrollably in the center of the plasma and spoil the energy confinement by excessive radiation. It has long been thought that the collisional transport of impurities in stellarators always leads to such accumulation (if the electric field points inwards, which is usually the case), whereas tokamaks, being axisymmetric, can benefit from "temperature screening", i.e. Read More

Ultracold plasmas (UCP) provide a well-controlled system for studying multiple aspects in plasma physics that include collisions and strong coupling effects. By applying a short electric field pulse to a UCP, a plasma electron center-of-mass (CM) oscillation can be initiated. In accessible parameter ranges, the damping rate of this oscillation is determined by the electron-ion collision rate. Read More

A highly elongated plasma is desirable in order to increase plasma pressure and energy confinement to maximize fusion power output. However, there is a limit to the maximum achievable elongation which is set by vertical instabilities driven by the $n=0$ MHD mode. This limit can be increased by optimizing several parameters characterizing the plasma and the wall. Read More

The energy of plasma waves can be moved up and down the spectrum using chirped modulations of plasma parameters, which can be driven by external fields. Depending on whether the wave spectrum is discrete (bounded plasma) or continuous (boundless plasma), this phenomenon is called ladder climbing (LC) or autoresonant acceleration of plasmons. It was first proposed by Barth \textit{et al. Read More

Within the problem of the finding of the mean potential energy of the charged particle in the plasma in this work a classification of physical systems (electrolytes, dusty plasmas, plasmas) is made based on consideration, or lack thereof, of a few special additional conditions. The system considered here, as well as other systems which are described with those additional conditions imposed are treated as the systems of the "closed" type, while the systems where those conditions are fully neglected - as being of the "open" type. In the our previous investigation one- and two component systems were examined. Read More

In fusion plasmas the strong magnetic field allows the fast gyro-motion to be systematically removed from the description of the dynamics, resulting in a considerable model simplification and gain of computational time. Nowadays, the gyrokinetic (GK) codes play a major role in the understanding of the development and the saturation of turbulence and in the prediction of the subsequent transport. Naturally, these codes require thorough verification and validation. Read More

Gas-puff imaging techniques are employed to determine the far SOL region radial electric field and the plasma potential in ICRF heated discharges in the Alcator C-Mod tokamak. The 2-dimensional velocity fields of the turbulent structures, which are advected by RF-induced $ \mathbf{E\times B} $ flows, are obtained via the time-delay estimation (TDE) techniques. Both the magnitude and radial extension of the radial electric field $ E_r $ are observed to increase with the toroidal magnetic field strength $ B_\varphi $ and the ICRF power. Read More

We investigate the nature of dissipative instability appearing in a prominence planar thread filled with partially ionised plasma in the incompressible limit. The importance of partial ionisation is investigated in terms of the ionisation factor and wavelength of waves propagating in the slab. To highlight the role of partial ionisation, we have constructed models describing various situations we can meet in solar prominence fine structure. Read More