Observation Of Multiple Broadband Alfvenic Chirping Modes In Hl-2a Nbi Plasmas

Multiple broadband Alfvenic chirping modes (CMs), with frequencies in the wide range of f similar to 35-150 kHz and chirping down rapidly, are found in HL-2A neutral beam injection plasmas, and the CMs can even coexist. The frequency chirping down process can be completed within similar to 1 ms, and the frequency shift can reach 30-50 kHz. The CMs propagate in ion diamagnetic drift directions poloidally. The toroidal mode number is confirmed to be n = 1, 2, 3 and 4 for the f similar to 35-65, 55-90, 70-120 and 100-150 kHz CMs, respectively. The CMs are more like to be energetic-particle continuum modes (EPMs), since the modes almost locate on the Alfven continuum.