Drift wave solitons and zonal flow: implications for staircase formation
The self-consistent nonlinear interaction of drift waves (DWs) and zonal flow (ZF) is investigated using nonlinear gyrokinetic theory, with both spontaneous excitation and beat-driving of ZF by DWs treated on the same footing. DW solitons are formed in nonlinear DW–ZF interactions and are confined b...
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| Main Authors: | , , , |
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| Format: | Article |
| Language: | English |
| Published: |
IOP Publishing
2025-01-01
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| Series: | Nuclear Fusion |
| Subjects: | |
| Online Access: | https://doi.org/10.1088/1741-4326/adc69f |
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| Summary: | The self-consistent nonlinear interaction of drift waves (DWs) and zonal flow (ZF) is investigated using nonlinear gyrokinetic theory, with both spontaneous excitation and beat-driving of ZF by DWs treated on the same footing. DW solitons are formed in nonlinear DW–ZF interactions and are confined between radially spaced micro-barriers induced by spontaneously excited ZF (SZF). The resulting radial structures in nonlinear DW–ZF interactions exhibit a similar pattern to the $\mathbf{E} \times \mathbf{B}$ ‘staircase’ observed in numerical simulations. These micro-barriers are generated by the repulsive response due to SZF, which, as a general property demonstrated in this work, also generates an attractive nonlinear potential in the DW equation. Meanwhile, the nonlinear potential due to beat-driven ZF is always attractive and, as such, always serves as a potential well to contribute to soliton formation. For SZF from initial noise, the simultaneous excitation of solitons and micro-barriers is found to be universal due to the zero-frequency nature of ZF and the spatial structure of the Reynolds stress. The present analysis thus provides a potential first-principles-based interpretation of the $\mathbf{E} \times \mathbf{B}$ staircase observed in simulations, which may contribute to the formation of micro transport barriers and enhance plasma confinement. |
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| ISSN: | 0029-5515 |