Pressure-gradient-induced Alfven eigenmodes: I. Ideal MHD and finite ion Larmor radius effects

TL;DR

This paper investigates how finite Larmor radius effects modify ideal MHD alpha-induced toroidal Alfven eigenmodes in high-beta tokamak plasmas, focusing on the Schrödinger equation solutions and potential well structures.

Contribution

It provides a detailed analysis of FLR effects on alpha-TAE modes, isolating these effects from kinetic compression, and describes their impact on eigenvalues and eigenfunctions.

Findings

FLR effects alter the Schrödinger potential and eigenfunctions of alpha-TAE modes.

Parameter scans reveal how FLR modifies mode stability and structure.

Results set the stage for identifying wave-particle resonance instabilities.

Abstract

In the second magnetohydrodynamic (MHD) ballooning stable domain of a high-beta tokamak plasma, the Schroedinger equation for ideal MHD shear Alfven waves has discrete solutions corresponding to standing waves trapped between pressure-gradient-induced potential wells. Our goal is to understand how these so-called alpha-induced toroidal Alfven eigenmodes alpha-TAE are modified by the effects of finite Larmor radii (FLR) and kinetic compression of thermal ions in the limit of massless electrons. In the present paper, we neglect kinetic compression in order to isolate and examine in detail the effect of FLR terms. After a review of the physics of ideal MHD alpha-TAE, the effect of FLR on the Schroedinger potential, eigenfunctions and eigenvalues are described with the use of parameter scans. The results are used in a companion paper to identify instabilities driven by wave-particle resonances in the second stable domain.