  Recent observations in HL-2A tokamak give new experimental evidences of
energetic particle mode (EPM) avalanche. In a strong EPM burst, the mode
structure propagates radially outward within two hundred Alfv\'en time, while
the frequency of the dominant mode changes self-consistently to maximize
wave-particle power exchange and mode growth. This suggests that significant
energetic particle transport occurs in this avalanche phase, in agreement with
theoretical framework of EPM convective amplification. A simplified relay
runner model yields satisfactory interpretations of the measurements. The
results can help understanding the nonlinear dynamics of energetic particle
driven modes in future burning plasmas, such as ITER.
