Sheared poloidal flow driven by mode conversion in tokamak plasmas.

Area of Science:

• Plasma physics
• Fusion energy research
• Magnetohydrodynamics

Background:

• Tokamak plasmas exhibit complex wave phenomena crucial for understanding fusion energy.
• Mode conversion processes, particularly near the ion-ion hybrid resonance, are key to energy deposition and plasma control.
• The role of poloidal magnetic fields in driving these wave dynamics has been an area of active investigation.

Purpose of the Study:

• To investigate the generation of poloidal forces resulting from mode conversion in tokamak plasmas.
• To analyze the influence of the poloidal magnetic field on wave propagation and damping.
• To quantify the resulting poloidal flows and compare them with experimental observations.

Main Methods:

• Utilizing a two-dimensional integral full-wave model to simulate wave behavior.
• Analyzing the transition from fast magnetosonic waves to slow ion cyclotron waves near the ion-ion hybrid resonance.
• Examining the impact of the poloidal field on the parallel wave spectrum and wave damping.

Main Results:

• Mode conversion near the ion-ion hybrid resonance is dominated by a fast magnetosonic to slow ion cyclotron wave transition.
• The poloidal magnetic field induces significant variations in the parallel wave spectrum, leading to localized wave damping.
• Poloidal forces generated in a narrow layer near the mode conversion surface drive sheared poloidal flows.

Conclusions:

• The study successfully models poloidal forces driven by mode conversion in tokamak plasmas.
• The findings highlight the significant role of the poloidal magnetic field in generating sheared poloidal flows.
• The calculated flows are comparable to those observed in ion Bernstein wave experiments, validating the model.