  We propose a phenomenological yet very general model in a form of generalized
complex Ginzburg-Landau equation to understand the dynamics of the
quasi-periodic fluid instabilities (called edge-localized modes) in the
boundary of toroidal magnetized high-temperature plasmas. The model reproduces
key dynamical features of the boundary instabilities observed in the
high-confinement state plasmas on the KSTAR tokamak, including quasi-steady
states characterized by field-aligned filamentary eigenmodes, transitions
between different eigenmodes, and rapid transition to non-modal filamentary
structure prior to the relaxation. It is found that the inclusion of
time-varying perpendicular sheared flow is crucial for reproducing the observed
dynamical features.
