Nonlinear Decay and Plasma Heating by a Toroidal Alfvén Eigenmode.

Area of Science:

• Plasma Physics
• Fusion Energy
• Magnetohydrodynamics

Background:

• Toroidal Alfvén eigenmodes (TAEs) are crucial for understanding energetic particle behavior in fusion plasmas.
• Nonlinear interactions of TAEs can lead to instability saturation and particle transport.

Purpose of the Study:

• To theoretically investigate the parametric decay of TAEs in toroidal plasmas.
• To identify the decay products and threshold conditions for this nonlinear process.

Main Methods:

• Theoretical analysis of plasma wave interactions.
• Derivation of the nonlinear wave coupling equations.
• Estimation of the threshold amplitude for parametric decay.

Main Results:

• Demonstrated that TAEs can parametrically decay into geodesic acoustic modes and kinetic TAEs.
• Estimated the threshold amplitude for this decay to be |δB⊥/B0|∼O(10−4).

Conclusions:

• The novel decay process contributes to the nonlinear saturation of TAE instabilities.
• This decay mechanism may also play a role in thermal plasma heating and transport regulation.