Recent 2D spatially and temporally resolved measurements of electron temperature fluctuations in the tokamak core have revealed new information on the dynamics of the sawtooth crash. Measures of poloidal localization of the reconnection zone are achieved through direct analysis of the 2D data and through an interpolated projection of the q = 1 region. An estimate of the toroidal coverage of the reconnection zone is achieved through analysis of shots exhibiting toroidal rotation in which the helically localized reconnection occurs both within and outside of the view of the measurement window. The localized trigger of the crash instability exhibits a dominant toroidal mode number of n ≈ 3, and a dominant poloidal mode number of m ≥ 10.
Externally driven magnetic field-line reconnection due to fast pulsed plasma current reversal in a Tokamak