A new, flux-balanced Hasegawa-Wakatani model

The modified Hasegawa-Wakatani (mHW) model [1] is the simplest two-field fluid model for the study of the interplay between drift waves and zonal flows. Unlike the Hasegawa-Mima (HM) model [2], the mHW model contains a drift wave instability, and unlike the original HW model, the mHW model describes the formation of robust zonal structures. However, a limitation of the mHW model is its treatment of the electron dynamics parallel to the magnetic field, which prevents it from converging to the modified HM (mHM) model [3] in the appropriate collisionless limit.

We present a new HW model with an improved treatment of the electron parallel dynamics to address this limitation, which we call flux-balanced HW (bHW) model. We demonstrate that the bHW model converges to the mHM model in the collisionless limit as desired, and has additional attractive properties, such as the development of uniformly stronger and more turbulent zonal jets than in the mHW model, and an enhanced variability in the turbulent fluctuations.

[1] R. Numata, R. Ball, and R. L. Dewar, Phys. Plasmas, 14, 102312 (2007)

[2] A. Hasegawa and K. Mima, Phys. Fluids, 21, 87 (1978)

[3] W. Dorland and G. W. Hammett, Phys. Fluids B 5, 812 (1993)