scholarly journals Linear simulation of kinetic electromagnetic instabilities in a tokamak plasma with weak magnetic shear

2021 ◽  
Vol 28 (1) ◽  
pp. 012107
Author(s):  
Yunchuan Zhao ◽  
Jiaqi Wang ◽  
Dongjian Liu ◽  
Wei Chen ◽  
Ge Dong ◽  
...  
Keyword(s):  
Tokamak Plasma ◽  
Magnetic Shear

Sheared slab ηi instability in tokamak plasma with negative magnetic shear

1998 ◽  
Vol 5 (4) ◽  
pp. 959-965 ◽  
Author(s):  
Jiquan Li ◽  
Lin Huang ◽  
Wenxiao Qu
Keyword(s):  
Tokamak Plasma ◽  
Magnetic Shear

Stability of a tokamak plasma with diffuse toroidal rotation

2020 ◽  
Vol 86 (5) ◽  
Author(s):  
O. E. López ◽  
L. Guazzotto
Keyword(s):  
Shooting Method ◽  
Tokamak Plasma ◽  
Solution Technique ◽  
Large Aspect Ratio ◽  
Internal Resonances ◽  
Flow Shear ◽  
Magnetic Shear ◽  
The Stability ◽  
External Kink ◽  
Selection Of

The present work considers the stability of a high- $\beta$ , large aspect ratio, circular plasma with diffuse profiles for the safety factor and the angular toroidal frequency (López & Guazzotto, Phys. Plasmas, vol. 24, 032501). An application of the Frieman–Rotenberg formalism results in a system of scalar eigenmode equations whose coupling is retained at the plasma–vacuum transition but is disregarded across the plasma column, which is a standard practice. The solution technique consists of a multidimensional shooting method for the poloidal harmonics; robust initial guesses are constructed by solving the dispersion relation in the static scenario with vanishing magnetic shear. Flow shear appears as a high- $\beta$ toroidal contribution, and we illustrate its destabilizing influence on $n=1$ external kink modes in the presence of ideal and resistive walls. Internal resonances are avoided by means of the selection of appropriate equilibrium parameters. The stabilizing influence of a finite positive average magnetic shear is also exemplified.

scholarly journals Field Line Pitch and Local Magnetic Shear in Tokamaks

1996 ◽  
Vol 49 (6) ◽  
pp. 1121
Author(s):  
JLV Lewandowski ◽  
M Persson
Keyword(s):  
Aspect Ratio ◽  
Field Line ◽  
Second Order ◽  
Tokamak Plasma ◽  
Magnetic Shear ◽  
Analytical Results

The field line pitch and its relation to the integrated magnetic shear is discussed for a low-β tokamak plasma. Analytical results using a second order inverse aspect ratio expansion are presented and specifically discussed in the limits of peaked and fiat current profiles. The results are compared and contrasted with an earlier calculation of the local magnetic shear.

Activated Prominences; Mechanisms for Activation and Eruption

1979 ◽  
Vol 44 ◽  
pp. 307-313
Author(s):  
D.S. Spicer
Keyword(s):  
Pressure Gradient ◽  
Density Gradient ◽  
Current Density ◽  
Convective Instability ◽  
Tearing Mode ◽  
Magnetic Shear ◽  
Long Wavelength ◽  
Ideal Mhd ◽  
Gradient Change ◽  
Accelerated Particles

A possible relationship between the hot prominence transition sheath, increased internal turbulent and/or helical motion prior to prominence eruption and the prominence eruption (“disparition brusque”) is discussed. The associated darkening of the filament or brightening of the prominence is interpreted as a change in the prominence’s internal pressure gradient which, if of the correct sign, can lead to short wavelength turbulent convection within the prominence. Associated with such a pressure gradient change may be the alteration of the current density gradient within the prominence. Such a change in the current density gradient may also be due to the relative motion of the neighbouring plages thereby increasing the magnetic shear within the prominence, i.e., steepening the current density gradient. Depending on the magnitude of the current density gradient, i.e., magnetic shear, disruption of the prominence can occur by either a long wavelength ideal MHD helical (“kink”) convective instability and/or a long wavelength resistive helical (“kink”) convective instability (tearing mode). The long wavelength ideal MHD helical instability will lead to helical rotation and thus unwinding due to diamagnetic effects and plasma ejections due to convection. The long wavelength resistive helical instability will lead to both unwinding and plasma ejections, but also to accelerated plasma flow, long wavelength magnetic field filamentation, accelerated particles and long wavelength heating internal to the prominence.

scholarly journals The Location of Magnetic Reconnection at Earth’s Magnetopause

2021 ◽  
Vol 217 (3) ◽  
Author(s):  
K. J. Trattner ◽  
S. M. Petrinec ◽  
S. A. Fuselier
Keyword(s):  
Magnetic Field ◽  
Solar Wind ◽  
Magnetic Reconnection ◽  
Ion Beams ◽  
Review Article ◽  
Observational Evidence ◽  
Magnetic Shear ◽  
General Direction ◽  
Shear Model ◽  
Wide Range

AbstractOne of the major questions about magnetic reconnection is how specific solar wind and interplanetary magnetic field conditions influence where reconnection occurs at the Earth’s magnetopause. There are two reconnection scenarios discussed in the literature: a) anti-parallel reconnection and b) component reconnection. Early spacecraft observations were limited to the detection of accelerated ion beams in the magnetopause boundary layer to determine the general direction of the reconnection X-line location with respect to the spacecraft. An improved view of the reconnection location at the magnetopause evolved from ionospheric emissions observed by polar-orbiting imagers. These observations and the observations of accelerated ion beams revealed that both scenarios occur at the magnetopause. Improved methodology using the time-of-flight effect of precipitating ions in the cusp regions and the cutoff velocity of the precipitating and mirroring ion populations was used to pinpoint magnetopause reconnection locations for a wide range of solar wind conditions. The results from these methodologies have been used to construct an empirical reconnection X-line model known as the Maximum Magnetic Shear model. Since this model’s inception, several tests have confirmed its validity and have resulted in modifications to the model for certain solar wind conditions. This review article summarizes the observational evidence for the location of magnetic reconnection at the Earth’s magnetopause, emphasizing the properties and efficacy of the Maximum Magnetic Shear Model.

Effects of nitrogen seeding in a tokamak plasma

2020 ◽  
Vol 27 (12) ◽  
pp. 122302
Author(s):  
Shrish Raj ◽  
N. Bisai ◽  
Vijay Shankar ◽  
A. Sen
Keyword(s):  
Tokamak Plasma

Effects of negative magnetic shear on toroidicity induced eigenmode instability in tokamaks

1997 ◽  
Vol 4 (4) ◽  
pp. 908-910 ◽  
Author(s):  
K. Rajendran ◽  
J. Q. Dong ◽  
S. M. Mahajan
Keyword(s):  
Magnetic Shear
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