EGAM Induced by Energetic-electrons and Nonlinear Interactions among EGAM, BAEs and Tearing Modes in a Toroidal Plasma

TL;DR

This paper reports the first experimental observation of energetic-electron-induced GAM (eEGAM) in HL-2A plasma, revealing nonlinear interactions among eEGAM, BAEs, and tearing modes, advancing understanding of plasma oscillation mechanisms.

Contribution

It provides the first experimental evidence of eEGAM induced by energetic electrons and details its nonlinear interactions with BAEs and tearing modes in a toroidal plasma.

Findings

eEGAM localized near q=2 surface in core plasma

eEGAM mode numbers are jm/nj=2/0

Nonlinear interactions among eEGAM, BAEs, and tearing modes observed

Abstract

In this letter, it is reported that the first experimental results are associated with the GAM induced by energetic electrons (eEGAM) in HL-2A Ohmic plasma. The energetic-electrons are generated by parallel electric fields during magnetic reconnection associated with tearing mode (TM). The eEGAM localizes in the core plasma, i.e. in the vicinity of q=2 surface, and is very different from one excited by the drift-wave turbulence in the edge plasma. The analysis indicated that the eEGAM is provided with the magnetic components, whose intensities depend on the poloidal angles, and its mode numbers are jm/nj=2/0. Further, there exist intense nonlinear interactions among eEGAM, BAEs and strong tearing modes (TMs). These new findings shed light on the underlying physics mechanism for the excitation of the low frequency (LF) Alfv\'enic and acoustic uctuations.