Long range avalanche-like electron heat transport events in the L-mode tokamak experiment*

Long range avalanche-like electron heat transport events are observed and analyzed in the L-mode tokamak experiment. We investigate avalanche dynamics and characteristics of the associated electron temperature (T_e) fluctuations in detail using the electron cyclotron emission imaging diagnostics on the KSTAR tokamak plasmas [1]. Initially, the mesoscale jet-like T_e profile corrugations appear. The long range avalanche-like event occurs with joint reflection symmetry when the T_e profile corrugations disappear and the associated T_e fluctuation power increases. In particular, the T_e gradient-correlated-fluctuation with the power law spectrum prevails during the avalanching periods. These observations suggest that the electron heat transport can be regulated by a mesoscale structure and dominated by the nondiffusive avalanche-like transport events in the L-mode plasma [2] when the significant MHD instabilities are absent. While the nonlinear gyrokinetic simulation is in progress, preliminary results of linear simulations will be provided.

[1] M. Choi et al., arXiv:1806.04947 (2018)

[2] G. Dif-Pradalier et al., Nucl. Fusion 57, 066026 (2017)