Drift wave turbulence and transport analysis of hot ion L-mode plasma with fishbone instability on the HL-3 tokamak
We establish the cross-scale coupling by which a fishbone mode governs both toroidal rotation and drift-wave turbulence in the HL-3 hot ion mode ($T_i \approx 3T_e$, $T_i(0)\approx9.8$\,keV). Combining multi-diagnostic measurements, OMFIT modeling, and TGLF simulations, we show that under 2.5\,MW co-injected NBI a steep fast-ion pressure gradient excites an $m=1,n=1$ fishbone mode. The mode redistributes resonant fast ions outward and decouples the NBI torque, and the sawtooth crash it triggers collapses the rotation from above $100$ to $60$\,krad/s. The same fast ions drive the fishbone and stabilize ion scale ITG/TEM turbulence. Their redistribution lowers the instability threshold and erodes the internal transport barrier. The effective ITG threshold combines a dominant temperature-ratio term, a fast-ion dilution factor, and an $E\times B$ shear term. TGLF scans show the high $T_i/T_e$ ratio suppresses all transport fluxes, synergistically with the fast-ion population. A single macroscopic MHD mode governs both momentum balance and microturbulence stability.