Abstract
Effects of the equilibrium plasma flow on the error field-driven tearing mode are investigated in a two-dimensional resistive magnetohydrodynamics model. It is found that nonlinear suppression of the tearing mode is dominated by the interaction between the magnetic island and the error field rather than the local flow shear on rational surfaces. For a small magnetic shear case, a modest rigid flow can counteract the driving effect of the error field on the mode in the early nonlinear growth stage and transform the error field-driven mode to a general tearing mode. For a large magnetic shear case, after a fast linear growth, the tearing mode will enter a saturated process quickly before the locked mode occurs, and the mode saturation level is reduced due to the magnetic island and error field pushing each other. The threshold flow strength and its scaling analysis for the saturated modes are also given in this paper.
Highlights
Boundary error field can drive the growth of the tearing mode (TM) and even cause major disruptions.1,2 In the weak magnetic shear configuration, the general TM is weak and unstable with small current gradient driving.3,4 In the reversed magnetic shear configuration, the large current gradient may lead to a fast growth or overlap with finite resistivity of the wall.5 how to suppress the driving effect of the error field on the TM for different magnetic configurations is a crucial problem in fusion plasma
We focus on the influence of the plasma flow on the error field-driving TM to further clear the role of magnetic shear and basic parametrical dependence of nonlinear saturation through the MHD simulation
It has been widely recognized that the plasma flow and error field have significant effects on resistive MHD instabilities
Summary
Boundary error field can drive the growth of the tearing mode (TM) and even cause major disruptions. In the weak magnetic shear configuration, the general TM is weak and unstable with small current gradient driving. In the reversed magnetic shear configuration, the large current gradient may lead to a fast growth or overlap with finite resistivity of the wall. how to suppress the driving effect of the error field on the TM for different magnetic configurations is a crucial problem in fusion plasma. How to suppress the driving effect of the error field on the TM for different magnetic configurations is a crucial problem in fusion plasma. A number of experimental studies have shown that the effect of the sheared plasma flow can decrease the growth rate of the TM.. The nonlinear simulation has shown that the mode has a strong coupling with the error field leading to fast growth and even global collapse when the locked mode occurs.. The suppression and nonlinear saturation of the error field-driving TM for different magnetic shears is still in question. We focus on the influence of the plasma flow on the error field-driving TM to further clear the role of magnetic shear and basic parametrical dependence of nonlinear saturation through the MHD simulation.
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