Comparative analysis of electrostatic and electromagnetic turbulence in HL-2A tokamak edge plasmas

Simultaneous measurements of electrostatic and electromagnetic turbulence have been conducted in low-beta ( β N ∼ 0.65 ) HL-2A plasmas using a reciprocating multi-probe array. Electrostatic fluctuation-driven particle flux exceeds electromagnetic-induced transport by 3–4 orders of magnitude. Electromagnetic turbulence in the 20–80 kHz range dominates particle transport while higher frequency electromagnetic fluctuations (80–200 kHz) show reduced impact, which contrasts with edge electrostatic turbulence. Time-resolved analysis of particle flux components reveals that phase coherence plays a dominant role in determining cross-field transport dynamics. Electromagnetic fluctuations demonstrate complex behavior as δ B r increases, with counteracting transport components Γ n e − B r and Γ v t − B r of comparable magnitude in opposing directions, which could necessitate adjustments to existing electromagnetic turbulence theories. Strong nonlinear interaction between electrostatic and electromagnetic turbulence is observed and experimental identification of Geodesic Acoustic Mode (GAM) signatures in both turbulence spectra. Concurrent coupling of magnetohydrodynamic activity and GAM with electrostatic fluctuations is confirmed, suggesting potential energy transfer mechanisms between these modes.