Predicting the Z-pinch Dimits shift through gyrokinetic tertiary instability analysis of the entropy mode

The Dimits shift, an upshift in the onset of turbulence from linear instability threshold, caused by self-generated zonal flows, can greatly enhance performance magnetic confinement plasma devices. Except simple cases, using fluid approximations and model geometries, this phenomenon has proved difficult to understand quantitatively predict. To bridge large gap complexity between models realistic treatment toroidal geometries (e.g. tokamaks or stellarators), present work uses fully gyrokinetic simulations a Z-pinch geometry investigate shift through lens tertiary analysis, which describes emergence drift waves zonally dominated state. Several features instability, previously observed models, are confirmed remain. Most significantly, efficient reduced-mode model, successful predicting gyrofluid limit (Hallenbert & Plunk, J. Plasma Phys. , vol. 87, issue 05, 2021, 905870508), is found be accurate here, with only slight modifications account for kinetic effects.