Sawtooth oscillations with the central safety factor,q0, below unity

Essential experimental features of sawtooth crashes are not explained by existing theories, especially the fact that ${\mathit{q}}_0$ remains well below unity throughout the sawtooth cycle. Here, a model consistent with experimental results is presented. The model considers the sawtooth crash as involving full reconnection of the magntiude field lines, leaving ${\mathit{q}}_0$<1. It leads to stronger plasma redistribution than the previous reconnection model; however, q(r) may remain almost unchanged. States with ${\mathit{q}}_0$ well below unity are shown to be possible results of different types of sawtooth crashes.