A sudden anomalous increase in the plasma resistivity at a magnetic neutral point is observed which results in fast energy dissipation and strong plasma heating. It appears earlier and its magnitude increases as (1) the plasma density is decreased, (ii) the discharge plasma current is increased, or (iii) the external quadrupole magnetic field is increased. When the sharp rise in the resistivity appears, the electron and ion temperatures rise abruptly up to the range of several keV within 0.5&mgr;secand about 10% of the initial energy stored in the capacitor (for the plasma current excitation) is converted into the ion thermal energy. This strong and efficient ion heating cannot be explained by a simple classical process and the role of turbulent waves should be important.