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An H-mode plasma state free of edge-localized mode (ELM), close to the L-Htransition with clear density and temperature pedestal has been observed bothat the Joint European Torus (JET) and at the ASDEX Upgrade (AUG) tokamaksusually identified by a low frequency (LFO, 1-2 kHz), m=1, n=0 oscillation ofthe magnetics and the modulation of pedestal profiles. The regime at JET isreferred to as M-mode while at AUG as intermediate phase or I-phase. Thiscontribution aims at a comparative analysis of these phenomena in terms of thedensity and temperature pedestal properties, the magnetic oscillations andsymmetries. Lithium beam emission spectroscopy (Li-BES) and reflectometermeasurements at JET and AUG show that the M-mode and the I-phase modulates theplasma edge density. A high frequency oscillation of the magnetics and thedensity at the pedestal is also associated with both the M-mode and theI-phase, and its power is modulated with the LFO frequency. The powermodulation happens simultaneously in every Mirnov coil signal where it can bedetected. The bursts of the magnetic signals and the density at the pedestalregion are followed by the flattening of the density profile, and by a radiallyoutward propagating density pulse in the scrape-off layer (SOL). The analysisof the helium line ratio spectroscopy (He-BES) signals at AUG revealed that theelectron temperature is modulated in phase with the density, thus the I-phasemodulates the pressure profile gradient. This analysis gave opportunity tocompare Li-BES and He-BES density profiles at different locations suggesting atoroidal and poloidal symmetry of the density modulation. The presented resultsindicate that the regimes, the AUG I-phase and the JET M-mode, exhibit similarcharacteristics, which leads to the conclusion that the regimes are likely thesame.

Identity of the JET M-mode and the ASDEX Upgrade I-phase phenomena