Gyrokinetic and experimental investigations of multi-scale turbulence in Alcator C-Mod and DIII-D plasmas

Extensive comparisons of high physics fidelity, multi-scale gyrokinetic simulations (m\textunderscore i/m\textunderscore e $=$ 60, realistic geometry, collisions, rotation, experimental inputs) with L-mode and ITER-relevant H-mode experiments have been performed on the Alcator C-Mod and DIII-D tokamaks. These simulations suggest that cross-scale interactions of ion and electron-scale turbulence play an important, even dominant, role in setting the experimental levels of both the ion and electron heat fluxes in reactor-relevant conditions. The validation of multi-scale gyrokinetic simulations has been extended further by comparing with turbulence measurements in reactor-relevant scenarios. Experiments on DIII-D in the ITER baseline scenario (H98$=$1, beta\textunderscore N $=$ 1.9, q95$=$3.3, Te\textasciitilde Ti ) documented possible signatures of cross-scale coupling in the wavenumber spectrum of intermediate-k (k*rho\textunderscore s \textasciitilde 2.5-5.0) density fluctuations measured with the Doppler backscattering (DBS) diagnostic. Results from multi-scale simulations of Alcator C-Mod plasmas and progress on analysis and simulation of the DIII-D experiments will be presented.