Effects Of Localized Current Drive On Tearing Mode Instability

Magnetic reconnection widely exists in the in the space and laboratory plasmas. It provides an efficient mechanism that magnetic energy transforms to the kinetic and heating energy. Tearing mode instability is a new kind of magnetic reconnection phenomena in consideration of limited resistance. The state of plasma can be seriously affected by tearing modes. Thus tearing mode instability is a kind of widely studied magnetohydrodynamic (MHD) instability and is a significant element leading to disruptions. The holistic restrained properties of plasma can be seriously affected by tearing modes. The tearing mode includes classical tearing modes and neoclassical tearing modes. The purpose of studying instabilities is to avoid their appear and control them when they has existed, which is considered to play an important role in plasma confinement. Radio frequency (RF) wave current drive is one of the main ways for control of tearing mode instability. RF waves are injected into plasma in the toroidal direction and RF waves push and drag electrons, and the movement of electrons is the driven current. This is the physical mechanism of RF wave current drive. RF wave current drive mainly includes ion cyclotron current drive (ICCD), Electron cyclotron current drive (ECCD), and lower hybrid current drive (LHCD). ECCD and LHCD are usually used to control tearing mode instabilities.A two-dimensional compressible MHD model in slab geometry is adopted to study the suppression effects of external localized current drive on the single tearing mode and double tearing mode. For single tearing mode, we focus on studying the late nonlinear phase of suppression effects of driven current on magnetic island and discussing the influences of depositional duration time of driven current. The effects of driven current on tearing mode in different stage are investigated as well. At present, there is still no research in suppression effects of external localized current drive on the double tearing mode existed in the advanced tokamaks. The suppression effect of external localized current drive on the double tearing mode is investigate in aspects of influences of depositional duration time and value of driven current too. It is found that the fast reconnection phase can be delayed rather than be avoided.