Electron fluid Effects on the explosive growth of double tearing modes

Yasutomo Ishii, Yasuaki Kishimoto
 
 We have reported the formation of a localized current structure, which
causes an explosive growth of MHD mode. This process was numerically
obtained for the nonlinear growth phase of double tearing modes (DTM) by
using nonlinear resistive MHD simulation. In the resistive MHD model,
usually, the reconnection region becomes Sweet-Parker type and the mode
growth rate depends on the resistivity. In the case of weakly coupled
DTM, however, the reconnection region is localized around the x-point
during the Rutherford type phase and then the mode enters the explosive
growth phase having the weak dependence on the resistivity. This feature
is roughly consistent with the experimentally observed tokamak plasma
disruption in reversed magnetic shear profiles. DTM are though as one of
the important MHD modes that cause the disruption of plasma confined by
tokamak device, especially in the advanced operational scenario. In such
high performance plasmas, however, plasma becomes collisionless and the
electron fluid effects become important, because of its high
temperature. In this study, we will show the electron fluid effects on
the formation of localized current structure and the explosive growth.