Solitary zonal structures in subcritical drift waves: a minimum model

Understand

Solitary zonal structures have recently been identified in gyrokinetic simulations of subcritical drift-wave (DW) turbulence with background shear flows.

• However, the nature of these structures has not been fully understood yet.
• Here, we show that similar structures can be obtained within a reduced model, which complements the modified Hasegawa-Mima equation with a generic primary instability and a background shear flow.
• We also find that these structures can be qualitatively reproduced in the modified Hasegawa-Wakatani equation, which subsumes the reduced model as a limit.