Core Turbulence Structures and $\rho_*$ Scaling Properties in H-Mode Plasmas

The characteristics of long-wavelength density fluctuations ($k_\perp\rho_i < 1$) are examined in the core region (0.5 $<$ r/a $<$ 0.9) of H-mode discharges and compared to turbulence in L-mode discharges. Measurements are obtained with the upgraded 16-channel (4-radial $\times$ 4-poloidal), high-sensitivity beam emission spectroscopy system at DIII-D. The $\rho^*$ scaling of turbulence structures in hybrid scenario H-mode plasmas demonstrates that the radial correlation lengths scale closely with the local ion gyroradius, as predicted theoretically and observed in L-mode plasmas. Eddy spatial structures, in contrast, differ dramatically between L and H-mode plasmas, with H-mode turbulence exhibiting a highly tilted structure in the radial-poloidal plane, as measured via 2D spatiotemporal correlations. Whether this difference results from flow-shear, radial propagation, or inherent turbulence dynamics will be investigated via comparison to measured flow shear, as well as with comparisons of GYRO simulations.