Electron Temperature Fluctuations in DIII-D SOL

We present an overview of electron temperature $T_e$ fluctuation properties in the scrape-off layer (SOL) of low (L) and high (H) confinement discharges, over L-H transitions, and during edge localized modes. $T_e$ fluctuations play an important role in the tokamak SOL, being responsible for the ``conductive'' (due to correlated fluctuations of $T_e$ and poloidal electric field $E_\theta$) part of the cross-field turbulent transport. In DIII-D, SOL $T_e$ fluctuations are measured using a harmonic technique deployed on the midplane reciprocating probe and having a bandwidth of up to 100 kHz. Relative $T_e$ fluctuation levels range from 0.1-0.2 inside the last closed flux surface (LCFS) to 0.3-0.5 in the SOL. $T_e$ fluctuations tend to be roughly in phase with the electron density $n_e$ fluctuations. ``Conductive'' and ``convective'' (due to correlated $n_e$ and $E_\theta$ fluctuations) components of the cross-field turbulent heat fluxes are comparable near the LCFS, while in the far SOL the convective component tends to be larger. Most of the $T_e$ fluctuation and heat flux spectral energy is below 50 kHz. Cross-field heat fluxes measured near the LCFS in L-mode are in reasonable agreement with the SOL power balance.