Nonlinear excitation of energetic particle driven geodesic acoustic mode by resonance overlap with Alfvén instability in ASDEX Upgrade

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Date
2025
Authors
Wang, Hao
Lauber, Philipp
Todo, Yasushi
Suzuki, Yasuhiro
Li, Hanzheng
Idouakass, Malik
Wang, Jialei
Adulsiriswad, Panith
Zoletnik, S.
Zohm, H.
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Nature Research
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Abstract
The Alfvén instability nonlinearly excited the energetic-particle-driven geodesic acoustic mode on the ASDEX-Upgrade tokamak, as demonstrated experimentally. The mechanism of the energetic-particle-driven geodesic acoustic mode excitation and the mode nonlinear evolution is not yet fully understood. In the present work, a first-principles simulation using the MEGA code investigated the mode properties in both the linear growth and nonlinear saturated phases. Here we show that the simulation successfully reproduced the excitation and coexistence of these two modes, and agreed with the experimental results well. Conclusive evidence showed that the resonance overlap is the excitation mechanism of the energetic-particle-driven geodesic acoustic mode. In the linear growth phase, energetic particles that satisfied different resonance conditions excited the Alfvén instability, which then caused energetic particle redistribution in phase space. These redistributed energetic particles caused resonance overlap, exciting the energetic-particle-driven geodesic acoustic mode in the nonlinear phase. © The Author(s) 2024.
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Controlled study , Growth curve , Simulation
Citation
Wang, H., Lauber, P., Todo, Y., Suzuki, Y., Li, H., Idouakass, M., Wang, J. and Adulsiriswad, P. (2025) 'Nonlinear excitation of energetic particle driven geodesic acoustic mode by resonance overlap with Alfvén instability in ASDEX Upgrade', Scientific reports, 15(1), p.1130. https://doi.org/10.1038/s41598-024-82577-3
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