scholarly journals Enstrophy non-conservation and the forward cascade of energy in two-dimensional electrostatic magnetized plasma turbulence

2020 ◽  
Vol 86 (4) ◽  
Author(s):  
G. G. Plunk
Keyword(s):  
Temperature Gradient ◽  
Plasma Turbulence ◽  
Magnetized Plasma ◽  
Larmor Radius ◽  
Ion Temperature ◽  
Fluid System ◽  
Ion Temperature Gradient ◽  
Zonal Flows ◽  
Electron Temperature Gradient ◽  
Enstrophy Cascade

A fluid system is derived to describe electrostatic magnetized plasma turbulence at scales somewhat larger than the Larmor radius of a given species. It is related to the Hasegawa–Mima equation, but does not conserve enstrophy, and, as a result, exhibits a forward cascade of energy, to small scales. The inertial-range energy spectrum is argued to be shallower than a $-11/3$ power law, as compared to the $-5$ law of the Hasegawa–Mima enstrophy cascade. This property, confirmed here by direct numerical simulations of the fluid system, may help explain the fluctuation spectrum observed in gyrokinetic simulations of streamer-dominated electron-temperature-gradient driven turbulence (Plunk et al., Phys. Rev. Lett., vol. 122, 2019, 035002), and also possibly some cases of ion-temperature-gradient driven turbulence where zonal flows are suppressed (Plunk et al., Phys. Rev. Lett., vol. 118, 2017, 105002).

A poloidal high-k scattering system for NSTX-U

2022 ◽  
Vol 17 (01) ◽  
pp. C01018
Author(s):  
C.W. Domier ◽  
J. Dannenberg ◽  
Y. Zhu ◽  
X. Liu ◽  
J.R. Sirigiri ◽  
...  
Keyword(s):  
Temperature Gradient ◽  
Far Infrared ◽  
Density Fluctuations ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Scattering System ◽  
Electron Temperature Gradient ◽  
High K ◽  
Electron Density Fluctuations ◽  
Scattering Volume

Abstract A previous 5-channel tangential high-k scattering system is being replaced by an 8-channel, poloidal high-k scattering system on the National Spherical Torus eXperiment Upgrade (NSTX-U) device located in Princeton, NJ, USA. The 693 GHz poloidal scattering system replaces a 280 GHz tangential scattering system to study high-k electron density fluctuations on NSTX-U, thereby considerably enhancing planned turbulence physics studies by providing a measurement of the k θ -spectrum of both electron temperature gradient (ETG) and ion temperature gradient (ITG) modes. Two approaches to generating the 693 GHz probe beam are under development: an optically-pumped far-infrared (FIR) laser that generates ∼50 mW, and a compact gyrotron that can potentially generate in excess of 5 W. Large aperture optics collect radiation scattered from density fluctuations in the plasma core at 8 simultaneous scattering angles ranging from 2 to 15° corresponding to poloidal wavenumbers that extend to >40 cm−1. Steerable launch optics coupled with receiver optics mounted on a 5-axis receiver carriage allow the scattering volume to be placed radially from r/a = 0.3 out to the pedestal region (r/a ∼ 0.99) and translated horizontally as needed to satisfy wavenumber matching.

Zonal flows and transport in ion temperature gradient turbulence

2002 ◽  
Vol 9 (12) ◽  
pp. 4911-4916 ◽  
Author(s):  
Sheikh Dastgeer ◽  
Sangeeta Mahajan ◽  
Jan Weiland
Keyword(s):  
Temperature Gradient ◽  
Ion Temperature ◽  
Ion Temperature Gradient ◽  
Zonal Flows
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