  Rare Alfv\'enic wave transitions between fixed-frequency and chirping phases
are identified in NSTX, where Alfv\'enic waves are normally observed to exhibit
either chirping or avalanching responses. For those transitions, we apply a
criterion [Duarte et al, Nucl. Fusion 57, 054001 (2017)] to predict the nature
of fast ion redistribution in tokamaks to be in the convective or diffusive
nonlinear regimes. For NSTX discharges in which the transition is not
accompanied by changes in the beam deposited power or modifications in the
injected radiofrequency power, it has been found that the anomalous fast ion
transport is a likely mediator of the bifurcation between the fixed-frequency
mode behavior and rapid chirping. For a quantitative assessment, global
gyrokinetic simulations of the effects of electrostatic ion temperature
gradient turbulence and trapped electron mode turbulence on chirping were
pursued using the GTS code. The investigation is extended by means of
predictive studies of the probable spectral behavior of Alfv\'enic eigenmodes
for baseline ITER cases consisting of elmy, advanced and hybrid scenarios. It
has been observed that most modes are found to be borderline between the steady
and the chirping phases.
