Quasilinear Modeling of Turbulent Transport of Microtearing Modes in the Pedestal

Predictive modeling of tokamak plasmas presents a significant challenge, particularly due to difficulties in modeling turbulent transport in the pedestal. Recent experimental evidence and gyrokinetic analysis has indicated that the microtearing mode (MTM) is responsible for substantial heat transport through the electron channel. Nonlinear gyrokinetic pedestal simulations are particularly challenging to perform and computationally expensive, so a reduced modeling is necessary to describe turbulent transport in the pedestal. In this work, we develop a mixing length model to estimate the electron heat flux caused by MTMs, where the mixing length is taken from linear gyrokinetic simulations. These local simulations are performed at the peak of the diamagnetic frequency profile; we then model the electron heat transport away from the peak with a Gaussian envelope. These simulations are complemented with global simulations in order to study mode widths and eigenmode structures. To verify these results, we use our model in tandem with the integrated modeling suite ASTRA and apply it to a variety of discharges.