Kinetic Simulations of the Sawtooth Crash

The core plasma in tokamaks is known to exhibit sawtooth oscillations when the q-axis drops below unity. In each sawtooth cycle, temperature, density, and current in the core increase gradually, followed by a rapid drop in these quantities. The rapid drop, known as the sawtooth crash, is attributed to magnetic reconnection. We study the sawtooth crash process in three-dimensions using a fully kinetic particle-in-cell method implemented in the PICTOR code. We discuss the differences and similarities between the kinetic simulations and the magnetohydrodynamic simulations with similar physical parameters. Specifically, we find development of significant phase-space anisotropy in the kinetic simulations, which are generally not incorporated in the MHD models.