A study of sawtooth phenomena in TEXT: Comparison between theory and experiment

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Abstract
Through a detailed analysis of soft-X-ray emissions from TEXT, comparisons were made between the observed phenomena and the often accepted theoretical model according to which a growing m = 1 mode is responsible for the sawtooth collapse. The sawtooth period was measured over a broad range of plasma conditions and compared with previously published theoretical and empirical scalings. The observed sawtooth period scaling was not found to depend strongly on the inversion radius, in contrast with previously published scalings. The time evolution of the often observed sinusoidal oscillations superimposed on sawteeth was analysed and compared with that predicted by Kadomtsev type reconnection sawtooth models. The sawtooth collapse is often in phase with the fall of the superimposed odd-m oscillation (assumed m = 1), but other cases show that the sawtooth collapse is independent of the phase of the m = 1 oscillations. Sawteeth in TEXT occur without clear m = 1 activity, and m = 1 oscillations occur before the crash, throughout the sawtooth period and after the crash, with the relative phase being independent of the collapse.
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