Investigating the Mode Structure of the Weakly Coherent Mode

The Weakly Coherent Mode (WCM, 200-500 kHz, $k_{\perp} \rho_s < 0.1$) is an edge phenomenon associated with I-mode, a steady state, ELM-free confinement regime that has been observed on the Alcator C-Mod, ASDEX-Upgrade, and DIII-D tokamaks. I-mode is characterized by high particle flux, creating a separation of transport channels that leads to the development of a temperature pedestal, but not a density pedestal. The WCM is thought to contribute to this increased particle flux, though its precise role in regulating edge transport is not well-understood. Here, we investigate the structure of the WCM, particularly regarding poloidal asymmetry, using data from poloidally- and toroidally-arrayed Mirnov coils, as well as phase contrast imaging, with radial profiles of $T_e$, $n_e$, and $\Phi$ in the scrape-off layer provided by the Mirror Langmuir Probe. The WCM phenomenology is then compared to that of the Quasi-Coherent Mode, the edge fluctuation responsible for exhausting impurities in the Enhanced D$_{\alpha}$ H-mode.