Published online by Cambridge University Press: 20 December 2006
Tokamak plasma with negative central current density is known to be unstable for m=1/n=0 resistive kink magnetohydrodynamic instability and the explanation for the absence of negative central current, the so-called current hole phenomena, is made by the destabilization of the mode. However, a strong reversed magnetic shear configuration has two resonant surfaces for low mode numbers and should be unstable for the double tearing mode (DTM). Here, we examine the effects of DTM on the formation of current hole and show that the occurrence of DTM does not change the situation completely. The growth of DTM flattens the current profile near the minimum-q region; here q is the safety factor, and the current gradient to drive n=0 mode usually remains after a reconnection event due to DTM and the stability of m=1/n=0 mode is not affected much by the DTM activity.