Effect of toroidal mode coupling on explosive dynamics of m/n=3/1 double tearing mode

The CLT code is used to quantitatively study the impact of toroidal mode coupling on the explosive dynamics of m/n = 3/1 double tearing mode. This work focuses on the explosive reconnection processes in which energy bursts and the main mode no longer dominates when the separation between two rational surfaces is relatively large in the medium range. The development of higher m and n modes is facilitated by a relatively large separation between two rational surfaces, a small qmin (the minimum value of safety factor), or a low resistivity. The relationships between the higher m and n modes development, explosive reconnection rate and the position exchange of 3/1 islands are summarized for the first time. The separation plays a more important role than qmin on enhancing the development of higher m and n modes. At a relatively large separation, the well development of higher m and n modes greatly reduces the reconnection rate, and suppresses the development of the main mode, resulting in the main mode not being able to develop sufficiently large to generate the position changes of 3/1 islands.