Observing Coupled Mode Dynamics Across Independent Diagnostics on HBT-EP

The core and edge structures of kink, tearing, and sawtooth crash instabilities have been studied across independent physical signatures at the HBT-EP tokamak. The Singular Value Decomposition is used to temporally correlate normalized spatial structures from independent diagnostics in selected time windows. This method is sufficiently robust to choices of signal filtering and composition, and can assist in analysis of nonlinear or coupled behaviors such as pre/postcursors to sawtooth crashes and rapidly evolving modes. Particular use is made of HBT-EP's spatially calibrated 4-array poloidal tomographic and two-color tangential EUV systems. These diagnostics permit us to observe rotating modes in many conditions, including 2/1 tearing modes coupled to edge 3/1 kink modes. New observations of sawteeth (see Boting Li this session) are supplemented by describing the MHD structures occurring before and after sawtooth crashes, and still unexplained observations include "bursting" coupled modes and fast MHD phenomena with very rapid amplitudes changes.