High-frequency fishbones at JET: theoretical interpretation of experimental observations

Abstract

The existence of fishbone fluctuations at frequencies comparable to those of geodesic acoustic modes (GAM) and beta induced Alfvén eigenmodes (BAE) has been demonstrated theoretically in a recent work (Zonca et al 2007 Nucl. Fusion 47 1588). Here, we show that observation of fishbones at unexpectedly high frequencies in JET (Nabais et al 2005 Phys. Plasmas 12 102509) is well interpreted as experimental evidence of high (GAM/BAE range) frequency fishbones and discuss the insights concerning both supra-thermal particles as well as thermal plasma properties that can be obtained from experimental observations.

Investigation of fast particle driven instabilities by 2D electron cyclotron emission imaging on ASDEX Upgrade

“…mode frequency, radial location and radial structure) point in the direction that these modes (at least the 2/1 modes) should be interpreted as BAEs [21][22][23], localized below the local minimum associated with the rational q surface in the Alfvén continuum. These modes might be the same as the bursting modes reported in [24] and [25] (where they were referred to as 'high frequency fishbones').…”

Linear dispersion relation of beta-induced Alfvén eigenmodes in presence of anisotropic energetic ions

“…A global stability analysis, involving WKB radial mode structure effects from finite θ k ≡ (nq ) −1 k r , modifies the GFLDR [29,30] and will be considered in a separated paper. Furthermore, the Λ term in the BAE dispersion relation does not include the deeply [15] and barely trapped particle dynamics, nor finite Larmor radius and finite magnetic-orbit width effects [14,46].…”

Observation of Low Frequency MHD Mode Driven by Energetic Particles in Large Helical Device Plasmas with Strong Interchange Mode Activities

“…The BAE excitation can be described using the generalized fishbone-like dispersion relation (GFLDR) [13,14,16]. The GFLDR developed by L. Chen & F. Zonca is used to study plasma dynamics with the frequency range from kinetic ballooning mode (KBM)/BAE to TAE.…”