Investigation of Trigger Mechanism in the Explosive Nonlinear Growth of the Double Tearing Mode

Magnetic reconnection dynamics due to the nonlinearly destabilized double tearing mode (DTM) is simulated, focusing on the nonlinear growth phase in the framework of reduced resistive magnetohydrodynamics (MHD). The nonlinearly explosive growth of the DTM accompanying fast magnetic reconnection is found to result from a secondary instability, the mechanism of which consists of the sequential unstable modulation due to twodimensional distortion of magnetic islands and modification of the nonlinear current profile. The trigger dynamics of the nonlinear growth phase is illustrated via the investigation of the evolution of both the kinetic and magnetic energies of the secondary instability.

在约化电阻磁流体动力学（MHD）框架下，对由非线性失稳的双撕裂模（DTM）引起的磁重联动力学进行了模拟，重点关注非线性增长阶段。研究发现，伴随快速磁重联的DTM的非线性爆发式增长是由一种二次不稳定性导致的，其机制包括由于磁岛的二维扭曲和非线性电流分布的改变所引起的连续不稳定调制。通过研究二次不稳定性的动能和磁能的演化，阐明了非线性增长阶段的触发动力学。